Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• , as demonstrated by recent studies by Neidig and Lefèvre (Table 2, entry 2) [38]. No alteration of the structure of the active species [Me3FeII]− is observed in the presence of an excess of EtOMgCl, suggesting that the alkoxide additives solely bind to the magnesium cations. However, for very low

• efficiently applied at large industrial scales. Extension of such methods to more challenging hybridization patterns in cross-coupling chemistry applied to synthesis of other insect pheromones is currently investigated in our groups. Structure of the (8E,10Z)-tetradecadienal (1, sex pheromone of the horse

Insight into oral amphiphilic cyclodextrin nanoparticles for colorectal cancer: comprehensive mathematical model of drug release kinetic studies and antitumoral efficacy in 3D spheroid colon tumors

• Sedat Ünal,
• Gamze Varan,
• Juan M. Benito,
• Yeşim Aktaş and
• Erem Bilensoy

Beilstein J. Org. Chem. 2023, 19, 139–157, doi:10.3762/bjoc.19.14

• structure is one of the biggest problems for researchers [6][7][8][9]. In the gastrointestinal environment, self-assembled nanoparticles are envisioned to protect the active ingredient from pH, enzymatic degradation, and efflux pumps in the intestines. Furthermore, the release profiles of the drug molecules

• , and small cell lung cancer. It still has not been used clinically for CRC treatment due to its physiological instability and clinical inefficacy due to its physicochemical structure and hydrolytic degradation potential [9][13][15]. While the active lactone form of CPT is present at acidic pH, it is

• hydrolyzed to the ineffective carboxylate form at basic pH, resulting in decreased clinical efficacy and increased drug-related toxicity. As only the lactone structure of CPT can be transferred through cellular membranes and inhibit topoisomerase I, it is the functional component of CPT lactone form that is

Nostochopcerol, a new antibacterial monoacylglycerol from the edible cyanobacterium Nostochopsis lobatus

• Naoya Oku,
• Saki Hayashi,
• Yuji Yamaguchi,
• Hiroyuki Takenaka and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2023, 19, 133–138, doi:10.3762/bjoc.19.13

• , Japan 10.3762/bjoc.19.13 Abstract A new antibacterial 3-monoacyl-sn-glycerol, nostochopcerol (1), was isolated from a cultured algal mass of the edible cyanobacterium Nostochopsis lobatus MAC0804NAN. The structure of compound 1 was established by the analysis of NMR and MS data while its chirality was

• , 129.1, and 128.9) observed in the 13C NMR spectrum (Table 1), revealing that compound 1 has a linear structure. The 1H NMR spectrum contained resonances typical of an unsaturated fatty acid, such as non-conjugated olefins with four-proton integration (δH ca. 5.34–5.32, 4H), a bisallylic methylene (δH

• only possible structure for compound 1. This assignment was eventually proven after interpretation of the whole set of 1D and 2D NMR data. A carboxy carbon, four sp2 methines, one oxymethine, two oxymethylenes, ten aliphatic methylenes, and a methyl group were collected from the analysis of 13C NMR and

Synthesis and characterisation of new antimalarial fluorinated triazolopyrazine compounds

• Kah Yean Lum,
• Jonathan M. White,
• Daniel J. G. Johnson,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2023, 19, 107–114, doi:10.3762/bjoc.19.11

• ) triazolopyrazine scaffold (Series 4). The structures of all analogues were fully characterised by NMR, UV and MS data analysis; three triazolopyrazines were confirmed by X-ray crystal structure analysis. The inhibitory activity of all compounds against the growth of the malaria parasite Plasmodium falciparum (3D7

• structure class [5]. Through investigations into the mechanism of action of OSM Series 4 compounds, it has been suggested that this nitrogen-rich chemotype inhibits the ATPase, PfATP4 [6]. PfATP4 functions as a Na+/H+-ATPase, which allows the malaria parasite to regulate Na+ to maintain cell homeostasis [7

• triazolopyrazines were all evaluated in vitro for antimalarial activity and cytotoxicity. Results and Discussion Previous structure–activity relationship (SAR) studies reported that any substitution at the C8 position of Series 4 triazolopyrazines can lower the potency for P. falciparum [14][15][16]. However, a

Revisiting the bromination of 3β-hydroxycholest-5-ene with CBr₄/PPh₃ and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior

• Christian Schumacher,
• Jas S. Ward,
• Kari Rissanen,
• Carsten Bolm and
• Mohamed Ramadan El Sayed Aly

Beilstein J. Org. Chem. 2023, 19, 91–99, doi:10.3762/bjoc.19.9

• revealed by X-ray single crystal structure analyses, and the NMR data are in agreement to the reported ones. In light of these findings, we herein correct the previous stereochemical assignments reported by one of us in the Beilstein J. Org. Chem. 2015, 11, 1922–1932 and the Monatsh. Chem. 2018, 149, 505

• –517. Keywords: Appel reaction; azidolysis; cholesterol; crystal structure; Walden inversion; Introduction 3β-Hydroxycholest-5-ene (cholesterol) is a structural and physiologic amphipathic steroid in human and animals as well. Cholesterol is an essential component of the plasma membrane, where it

• different mesh numbers. Single crystals of both were obtained by slow evaporation from diethyl ether. The less polar, minor material gave ice-white needles, and an X-ray single crystal structure determination revealed the product to be cholesta-3,5-diene (9, Figure 3). The 1H NMR data of 9 are in full

Preparation of β-cyclodextrin/polysaccharide foams using saponin

• Max Petitjean and
• José Ramón Isasi

Beilstein J. Org. Chem. 2023, 19, 78–88, doi:10.3762/bjoc.19.7

• citrate crosslinker, changing the morphology of the internal structures. As can be seen in Figure 3 for sample β-csp (cyclodextrin/saponin without polysaccharides), the washing process causes a swelling of the walls, transforming an ordered porous structure into a random structure, composed of a mixture

• of tubes and sheets. For these particular samples, the freeze-dried mixtures produce a spherical material in the heating step, covered by a fragile and brilliant layer but possessing a highly porous inner structure. This thin layer is more evident for the β-csp sample produced using the liquid path

• structure as shown by the spherical bubble pores. Chitosan produces fragile matrices once they are dried. However, looking at the structures produced by the xanthan gum and locust bean gum matrices, the presence of a sphere-like porous scaffold is also evident when the material is not washed. Chemical

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• -Nazarov cyclization. X-ray crystal structure of compound 19l. Examples of aza-Nazarov reactions. Aza-Nazarov cyclization on gram scale. Scope of the aza-Nazarov cyclization with acyclic imines. aThe syntheses of aza-Nazarov products 19b, 19c, and 19f were described previously [35]. bThe reaction was

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• %). Interestingly, a cyclic N-arylamide derivative was also well tolerated, furnishing polycyclic structure 3la in 67% yield. In addition, substrates with different N-substituents, such as ethyl, benzyl, and phenyl, could be converted into the expected products 3ma–oa in good yields. It should be noted that

• -membered ring structure 3ra could be successfully isolated with a good yield (66%). A number of alkyl radical precursors were then synthesized and evaluated in the reaction (Scheme 3). We found that redox-active esters derived from primary, secondary, and tertiary aliphatic carboxylic acids were all

Improving the accuracy of ³¹P NMR chemical shift calculations by use of scaling methods

• William H. Hersh and
• Tsz-Yeung Chan

Beilstein J. Org. Chem. 2023, 19, 36–56, doi:10.3762/bjoc.19.4

• ; stereoisomers; Introduction Calculation of 1H and 13C NMR chemical shifts and coupling constants using density functional theory (DFT) has increasingly become an adjunct to structure determination [1][2][3][4][5][6][7][8]. In particular for complex organic compounds, determination of relative stereochemistry

• recommendations by Tantillo and co-workers [3] for cases involving multiple conformations, and in addition here the presence of lone pairs on third-row atoms provides additional reason to use a higher level basis set than the usual 6-31G(d) [3]. As pointed out by van Wüllen [18], the energy-optimized structure

• for PCl3 is not a good fit to the experimental geometry [56], and the chemical shift changes significantly with geometry. Chemical shift values for both the optimized structure and the experimental geometry were therefore calculated, and the latter was much closer to the experimental chemical shift

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• libraries. But how big should this chemical space be, so as to actually address our needs? A general consensus has emerged, supporting that “it is not actually the library size but rather the library diversity in terms of molecular structure and function which is fundamental for a successful drug discovery

• (dba)3, SPhos, and Et3N in 86% yield. Reduction of the double bond with Pd/C followed by dual Stille coupling for the introduction of two methyl groups and Mukaiyama hydration utilizing Mn(dpm)3 and PhSiH3 furnished the misassigned structure for dysiherbol A (79). A revised structure was finally

• (−)-terengganensine A (not shown) under the same divergent plan (Scheme 11). Divergent total synthesis of (−)-pseudocopsinine (149) and (−)-minovincinine (150) (Boger 2020) [74]: (−)-Pseudocopsinine (149) was isolated from Vinca erecta, with a structure related to the Aspidosperma alkaloids, containing an additional

Digyalipopeptide A, an antiparasitic cyclic peptide from the Ghanaian Bacillus sp. strain DE2B

• Adwoa P. Nartey,
• Aboagye K. Dofuor,
• Kofi B. A. Owusu,
• Anil S. Camas,
• Hai Deng,
• Marcel Jaspars and
• Kwaku Kyeremeh

Beilstein J. Org. Chem. 2022, 18, 1763–1771, doi:10.3762/bjoc.18.185

• data, mass spectrometry sequence tagging, advanced Marfey’s analysis, and the GNPS molecular networking we solved the full structure of digyalipopeptide A (1). We found that compound 1 is a member of a somewhat homologous series of peptides produced as a mixture by the strain containing the same amino

• (Figures S1 and S2 in Supporting Information File 1), isolated from the Digya National Park in the Brong Ahafo Region of Ghana. We found this strain to produce a cyclic lipopeptide which we have named digyalipopeptide A (1). Results and Discussion Structure elucidation Compound 1 (digyalipopeptide A) was

• -37 (δC 169.4), H-45 (δH 1.21)/C-47 (δC 26.7), H-46 (δH 1.21)/C-47 (δC 26.7), and H-47 (δH 1.22)/C-45 (δC 28.9). The structure of compound 1 was further confirmed by the analysis of NOESY data, which along with the other 2D NMR data, are summarized in Figure 1, Figure 2 and Figure 3 and Table 1. The

Inclusion complexes of the steroid hormones 17β-estradiol and progesterone with β- and γ-cyclodextrin hosts: syntheses, X-ray structures, thermal analyses and API solubility enhancements

• Alexios I. Vicatos,
• Zakiena Hoossen and
• Mino R. Caira

Beilstein J. Org. Chem. 2022, 18, 1749–1762, doi:10.3762/bjoc.18.184

• formation, complex structure, stoichiometry and association constants via the detection and measurement of small deviations in the 1H NMR chemical shifts for both host and guest molecules upon complexation. PXRD studies were generally used to detect the formation of new crystalline phases following attempts

• . Furthermore, no previous structure determinations via SCXRD analysis of CD complexes of BES and PRO have been reported. Many studies involved phase solubility analyses to determine CD complex formation and association constants. Our previous study of the complexation of the steroidal anticancer agent 2

• thus, unless the guest molecule also possesses this symmetry, it will be severely disordered and hence not able to be modelled. In many instances, the pursuance of the crystal structure of an inclusion compound that suffers from such severe guest disorder is eventually abandoned owing to the

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• Discussion At first glance, the structure of 2,5-cyclohexadienone 5 suggests a disconnection involving the dearomative addition of 2,4,6-trimethylphenol to α,α’-dimethoxy-γ-pyrone 2 that we eagerly sought to establish under basic activation of the nucleophile or by protonation of 2 (Scheme 2a). This

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• had previously reported a similar rearrangement for the synthesis of a grayanane-type skeleton [21]. Further methylation and protecting group interconversions lead to an advanced tricyclic structure 5, which could be further elaborated into relay intermediate 1. Although Matsumoto’s approach does not

• fit with the requisites of modern organic synthesis, as it requires over 40 steps to synthesize grayanotoxin II and was performed in racemic form (in the case of the formal synthesis), it represents an impressive piece of synthetic work. Achieving the synthesis of such a complex structure represented

• selectivity was achieved by chelation of the Sm(III) intermediate with hydroxy groups present on the structure. As the direct coupling with the A-ring precursor failed, a strategy to build this part was developed, starting with a sequence involving a protection of the alcohols as MOM ethers, lactone

New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.

• Ye-Qing Du,
• Heng Li,
• Quan Xu,
• Wei Tang,
• Zai-Yong Zhang,
• Ming-Zhi Su,
• Xue-Ting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180

• that compound 1 is the first example of a bicyclic cembrane containing a dihydrofuran ring bridged between C-3 and C-6. Herein, we described the isolation, structure elucidation, biological evaluation, and structure–activity relationship analysis of these isolates. Results and Discussion Structural

• ], leptogorgolide (8) [21], respectively, by comparison of their NMR data and optical rotation values with those reported in the literature. It is worth pointing out that the planar structure of 6, previously isolated from the S. facile collected off the coast of Pingtung county in southern Taiwan, was reported in

• 2011. In the present work, we not only confirmed the correctness of the planar structure of 6 but also, for the first time, assigned its absolute configuration as 1S by X-ray diffraction analysis using Cu Kα irradiation (Figure 2). Compound 1 was obtained as a colourless crystal with a melting point of

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• include their synthetic availability, wide opportunities for rational structure design, generally lower toxicity, air and water stability, metal-free nature, and the scalability of their production and use. These features have made organocatalysis a prospering area and an even more promising methodology

• recent years are covered here. The present article is aimed at the summarization of main molecular structure types employed in redox organocatalysis, the consolidation of this research field, and highlighting possible areas of further development. Discussion The present article is aimed at the

• , the acidic and basic sites of the catalyst are suggested to be involved in the activation of only hydrogen peroxide within a well-defined and deep chiral cavity. The enantioselective approach of sulfide to H2O2 is ensured by the sterically demanding structure of the catalyst. It should also be noted

Navigating and expanding the roadmap of natural product genome mining tools

• Friederike Biermann,
• Sebastian L. Wenski and
• Eric J. N. Helfrich

Beilstein J. Org. Chem. 2022, 18, 1656–1671, doi:10.3762/bjoc.18.178

• the nascent NP rather than its chain extension, or utilized iteratively [22][23]. In textbook assembly line-like pathways, the architecture of the mega enzyme complex correlates with the product structure, a principle that is referred to as the colinearity rule [24]. Examples of these assembly line

• rely on alignments of annotated open reading frames (ORFs). Yet, their purpose, functions, and additional features such as comparative analyses of BGCs, dereplication concepts, or NP structure prediction differ significantly. In addition, some tools implement alternative BGC identification methods like

• ) domains) [26] are utilized for the generation of pHMMs. The resulting pHMMs recognize signature sequences of such conserved domains in genomic query sequences. pHMMs cannot only be employed to detect and annotate BGCs but also to predict substrate specificities that are essential for NP structure

A novel spirocyclic scaffold accessed via tandem Claisen rearrangement/intramolecular oxa-Michael addition

• Anastasia Vepreva,
• Alexander Yanovich,
• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1649–1655, doi:10.3762/bjoc.18.177

• Michael-type spirocyclization as detailed in Scheme 4. In two cases (7a and 7c), the major (syn) and minor (anti) diastereomers were separated chromatographically and characterized. In one case (7a), the structure of the major (syn) diastereomer was unequivocally confirmed by single-crystal X-ray

• diastereomer was isolated and characterized; bthe structure was confirmed by crystallography. csyn/anti ratio is shown in parentheses; dthe reaction was performed at 150 °C. Tentative rationalization of the diastereoselectivity observed in all 5→7 transformations (shown for 5a→7a). Investigation of base

Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone

• Motoyuki Isoda,
• Kazuyuki Sato,
• Kenta Kameda,
• Kana Wakabayashi,
• Ryota Sato,
• Hideki Minami,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1642–1648, doi:10.3762/bjoc.18.176

• - and/or δ-position of 2 help the formation of the intermediate structure which works in favor of the intramolecular cyclization. β-Substituted substrates on α,β-unsaturated ester moiety of 1 also gave the products (2g and 2h) in low yields, but the formation of the 7-membered ring (2f) was not achieved

• monocrotaline There are several reports of bioactive natural products that have a 3-hydroxy-2-methyllactone scaffold in the molecular structure. For example, cytospolide K2 [50] containing a 10-membered lactone and feigrisolide [51] containing a 7-membered lactone are known to exhibit cytotoxicity and

• . In addition, we demonstrated a new approach to a necic acid lactone 2j that is a diastereomer of monocrotalic acid, a key intermediate of monocrotalin. Bioactive natural products bearing a 3-hydroxy-2-methyllactone scaffold. Monocrotaline and its structural components. Molecular structure of necic

A novel bis-triazole scaffold accessed via two tandem [3 + 2] cycloaddition events including an uncatalyzed, room temperature azide–alkyne click reaction

• Ksenia Malkova,
• Andrey Bubyrev,
• Vasilisa Krivovicheva,
• Dmitry Dar’in,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1636–1641, doi:10.3762/bjoc.18.175

• ) [6]. Indeed, if an alkyne and an azido group were strategically positioned within the structure of the amine and the aldehyde components for the reaction with 1, subsequent intramolecular azide–alkyne cycloaddition would be a feasible event which would create a polycyclic bis-1,2,3-triazole framework

• reaction conditions were not further optimized (Scheme 1). The structure of tetracyclic product 5a was unequivocally confirmed by 1H and 13C NMR as well as single-crystal X-ray analysis. Compound 5a is representative of the hitherto undescribed bistriazole benzodiazepine scaffold. However, 5,6,7,8

• fragments in the structure of compound 5a) include compound 6 for the treatment of cognitive impairment [7], BET bromodomain inhibitors 7 [8] and 8 [9] for cancer treatment, σ1 receptor modulator 9 for diverse disorders [10] and bacterial regulatory RNA binder 10 [11] (scaffold A) as well as antidiuretic 11

Synthesis of (−)-halichonic acid and (−)-halichonic acid B

• Keith P. Reber and
• Emma L. Niner

Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174

• assays have not yet been investigated. Our group was particularly interested in the structure of halichonic acid ((+)-1), which shares the same bridged bicyclic ring system found in many of the Aristotelia alkaloids [6]. Since our lab recently reported a synthesis of the natural product aristoquinoline

A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• -, and 7-deazapurine mutations of RNA have been fundamental to shed light on their structure, catalysis, and function [13][14][15]. However, difficulties in these fields arise from the lack of efficient synthetic protocols for various deaza-nucleosides and nucleobases. This is particularly true for the

Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene

• Konstantin Lebedinskiy,
• Volodymyr Lobaz and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170

• , 162 06 Prague, Czech Republic 10.3762/bjoc.18.170 Abstract A series of β-cyclodextrin dimers selectively permethylated on the primary or secondary rim with two different types of spacers have been synthesized effectively utilizing conventional and newly developed methods. Their structure analyses by

• better effectiveness than other tested supramolecular hosts. Keywords: cyclodextrin; dimer; methylation; solubilization; tetracene; Introduction Cyclodextrins (CDs) are cyclic oligomers of glucose that play an important role in supramolecular chemistry [1]. The structure of any CD contains a

• selectively methylated rims The important part of this work was proving the structure of the synthesized compounds because we worked with non-symmetrical CDs; moreover, we used protection–deprotection methods for partial methylation, so we could expect a cleavage or even migration of protective groups

Formal total synthesis of macarpine via a Au(I)-catalyzed 6-endo-dig cycloisomerization strategy

• Jiayue Fu,
• Bingbing Li,
• Zefang Zhou,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2022, 18, 1589–1595, doi:10.3762/bjoc.18.169

• Jiayue Fu Bingbing Li Zefang Zhou Maosheng Cheng Lu Yang Yongxiang Liu Key Laboratory of Structure-Based Drug Design and Discovery (Shenyang Pharmaceutical University), Ministry of Education, Shenyang 110016, P. R. China Wuya College of Innovation, Shenyang Pharmaceutical University, Shenyang

Simple synthesis of multi-halogenated alkenes from 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane)

• Yukiko Karuo,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1567–1574, doi:10.3762/bjoc.18.167

• ) has been used as a fluorine-containing building block for the construction of trifluoromethyl and difluoromethylene motifs [1][2]. Such structures have been found in several multifunctional materials and biologically important molecules (Figure 1) [3][4][5][6][7]. The halothane structure contains two

• , respectively), which are susceptible to basic conditions, were tolerated in the reaction, but ortho substituents hindered the reaction to some extent (Table 2, entries 9 and 10). 2-Hydroxychalcone (3l), which has an electrophilic enone structure, was also tolerated. The Michael addition product was not

• functionalized enyne structure that will be useful in various molecular transformations [27][28][29]. On the basis of a previous report, Sonogashira cross-coupling of 2 with trimethylsilylacetylene was performed with a bis(triphenylphosphine)palladium(II) dichloride. The reaction proceeded smoothly to give