Enantioselective Diels–Alder reaction of anthracene by chiral tritylium catalysis

• Qichao Zhang,
• Jian Lv and
• Sanzhong Luo

Beilstein J. Org. Chem. 2019, 15, 1304–1312, doi:10.3762/bjoc.15.129

• α-ketoesters 4 was subjected to the reaction with anthracene (3a) to give the desired cycloadducts 5a–n in moderate to good yields and with up to 93% ee. The bulkier isopropyl ketoester resulted in a lower yield and enantioselectivity (Table 2, entry 3 vs 1 and 2). Variations on the aromatic group

An efficient synthesis of the guaiane sesquiterpene (−)-isoguaiene by domino metathesis

• Yuzhou Wang,
• Ahmed F. Darweesh,
• Patrick Zimdars and
• Peter Metz

Beilstein J. Org. Chem. 2019, 15, 858–862, doi:10.3762/bjoc.15.83

• ylide 21 [8] followed by alkyne generation [23] with butyllithium in a one-pot process, trienyne 3 was obtained as a 1.6:1 mixture of E and Z olefin isomers. Due to the presence of the isopropyl group at the disubstituted alkene [24] of 3, 30 mol % of the second generation Grubbs catalyst 22 were

An improved synthesis of adefovir and related analogues

• David J. Jones,
• Eileen M. O’Leary and
• Timothy P. O’Sullivan

Beilstein J. Org. Chem. 2019, 15, 801–810, doi:10.3762/bjoc.15.77

• wondered if alkylation of adenine with advanced intermediate 14 might represent a facile route to 6 (Figure 3). Holý and co-workers have previously utilised a similar alkyl chloride reagent to access adefovir analogues, but found that recourse to an isopropyl ester intermediate was necessary as the

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• pyridine group (Figure 1) recently released to the market. It has been experimentally established that the catalysts with an O-isopropyl group in their structure usually show the best combination of stability and activity. However, the oxygen atom having only one site for modification (i.e., the alkyl

Tuning the stability of alkoxyisopropyl protection groups

• Zehong Liang,
• Henna Koivikko,
• Mikko Oivanen and
• Petri Heinonen

Beilstein J. Org. Chem. 2019, 15, 746–751, doi:10.3762/bjoc.15.70

• reported were 10 minutes in an acetate buffer at pH 4.18 and approximately 4 minutes at pH 3.22. These values are close to an order of magnitude longer than what we determined for MIP 4a, and two orders of magnitude longer than those of the cyclohexyl and isopropyl analogs 4c, 4d (Table 1). It must be

• , d: R = isopropyl, e: R = CH2CF3. Proposed acetal hydrolysis pathways. Half-lives of 5’-acetal (4a–e) and 3’-acetal-protected (7a,c–e) 2’-deoxythymidines, and 2’-deoxy-3’-O-propen-2-ylthymidine (8b) in acetate (pH 4.94), citrate (pH 5.61) and phosphate (pH 6.82) buffers at 25.0 °C. The ionic strength

Selective benzylic C–H monooxygenation mediated by iodine oxides

• Kelsey B. LaMartina,
• Haley K. Kuck,
• Linda S. Oglesbee,
• Asma Al-Odaini and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55

• decatungstate [58]. Substrates containing tertiary C–H bonds, such as 1-isopropyl-4-methylbenzene (6b), were essentially unreactive under the developed conditions, returning starting alkyl arene with only a trace of acetoxylated product 7b (see Supporting Information File 1, Figure S11) [59]. Previous work on

LCST phase behavior of benzo-21-crown-7 with different alkyl chains

• Yan Deng,
• Xing Li,
• Qiao Zhang,
• Zheng Luo,
• Chengyou Han and
• Shengyi Dong

Beilstein J. Org. Chem. 2019, 15, 437–444, doi:10.3762/bjoc.15.38

• mg/mL (44.2 °C). It is demonstrated that, the longer the alkyl chain is the lower Tcloud becomes. We also found that the presence of a propyl substituent (3a) and an isopropyl group (3b) results in a quite different critical transition temperature, with Tcloud at 62.1 °C and 41.5 °C, respectively

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• that observed for 7a/7’a. Other substituents were tolerated on the phosphorus atom including an isopropyl or a cyclohexyl group and the corresponding phosphine oxides 7h/7’h and 7i/7’i were isolated in good yields. Increasing the steric hindrance around the phosphorus atom resulted in a higher

• diastereoselectivity. However, the sigmatropic rearrangement of the highly hindered di(tert-butyl)phosphinite 6j and tetra(isopropyl) phosphorodiamidite 6k did not occur (Scheme 7) [37]. The mechanism proposed by Rubin et al. involves a reversible addition of the Lewis base (DBU) on the cyclopropene double bond at C2

A novel and efficient synthesis of phenanthrene derivatives via palladium/norbornadiene-catalyzed domino one-pot reaction

• Yue Zhong,
• Wen-Yu Wu,
• Shao-Peng Yu,
• Tian-Yuan Fan,
• Hai-Tao Yu,
• Nian-Guang Li,
• Zhi-Hao Shi,
• Yu-Ping Tang and
• Jin-Ao Duan

Beilstein J. Org. Chem. 2019, 15, 291–298, doi:10.3762/bjoc.15.26

• . Therefore, it is speculated that the intrinsic electronic properties of aryl iodides makes no difference in this process. The reaction of methoxy-, 2-ethyl-, 2-isopropyl, and 2-phenyliodobenzenes in this procedure afforded the desired products in excellent yields (y-3, y-5, y-6 and y-4), while 1

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

• Teresa Mena-Barragán,
• José L. de Paz and
• Pedro M. Nieto

Beilstein J. Org. Chem. 2019, 15, 137–144, doi:10.3762/bjoc.15.14

• biosynthesis of this polymer. The presence of aromatic rings, such as the 4-methoxyphenyl group at the anomeric position, should be avoided because these groups can significantly modify the binding mode between the CS and the enzymes. For this reason, we introduced an isopropyl group in β-position of the

• anomeric center of the glycosyl acceptor. We hypothesized that the isopropyl moiety would not affect the CS–enzyme interaction. Trichloroacetimidate 12 was obtained by oxidative removal of the 4-methoxyphenyl group with CAN at 0 ºC and further treatment with trichloroacetonitrile and catalytic amounts of

• DBU. The glycosylation reaction with 2-propanol using TMSOTf as Lewis acid at 0 ºC cleanly provided the β-isopropyl glycoside 13 in 65% yield. Interestingly, no α-anomer was detected in the reaction mixture. Finally, cleavage of the levulinyl group using hydrazine monohydrate in pyridine/acetic acid

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• . Catalyst 154 containing an N-isopropyl group (Figure 29), which is considered to be sterically equivalent to the N-trifluoromethyl group, disclosed a substantially lower selectivity in both alternating copolymerization and ethenolysis reaction, underlining that the electronic effect determined by the

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• molecules 8–10, in 60%, 53% and 49% yields, respectively. Such well-known π-nucleophiles as phenols could be used for the reaction, though 3-methoxyphenol and 3,5-dimethoxyphenol gave inseparable mixtures of regioisomers 11a and 11b (NMR, LCMS). The reactions with p-isopropyl- and p-tert-butylphenols gave

The activity of indenylidene derivatives in olefin metathesis catalysts

• Maria Voccia,
• Steven P. Nolan,
• Luigi Cavallo and
• Albert Poater

Beilstein J. Org. Chem. 2018, 14, 2956–2963, doi:10.3762/bjoc.14.275

• with ortho-methyl and isopropyl groups at both ortho positions of their phenyl ring. DFT results highlight the more sterically demanding indenylidenes have to undergo a more exothermic first phosphine dissociation step. Overall, the study emphasises advantages of increased steric hindrance in promoting

• or isopropyl groups at the ortho positions of the phenyl substituent, compared to the unsubstituted 1 and 2. Comparing IMes vs SIMes, the activation is about 1 kcal/mol more favoured for the unsaturated system [42][43]. The absolute difference of 1 kcal/mol is maintained throughout the mechanism

• , however, we must point out that the opening of the metallacycle requires only 0.6 kcal/mol for the SIMes system versus 1.7 kcal/mol for the unsaturated system. The methyl and isopropyl-substituted indenylidene moieties reveal a different performance between the SIMes and the IMes congeners. When the

Synthesis of eunicellane-type bicycles embedding a 1,3-cyclohexadiene moiety

• Alex Frichert,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2018, 14, 2461–2467, doi:10.3762/bjoc.14.222

• the ring system and the adjacent atoms are located almost in plane, whereas the isopropyl group and ring carbons C3 and C4 are located on opposite sides of that plane. Since the oxidation/reduction sequence has affected the configuration at C2, diastereomer 19 is assigned the configuration (2S,3S,14R

• ). For diastereomer 19, 2-H did not show a NOESY correlation to 5-Hβ, but instead a correlation to 14-H, to the isopropyl methine hydrogen, and to 3-CH3. In addition, 3-CH3 correlates with both methylene hydrogens at C4. We found only two conformers of the (2S,3S,14R) diastereomer that meet those

• carbon following the ethoxycarbonylation. The 3JHH coupling constant proved that the isopropyl and ethoxycarbonyl groups both assume an equatorial position in a chair conformation. We were not able to obtain an X-ray analysis of cyanohydrin 22, but of one diastereomer (30) of an analog where the OTBS was

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• pyrones 44a–g in good-to-high yields within 1 h (Scheme 40). Ester, ketone, and hydroxy groups were tolerated in the reaction. In the case of an unsymmetrical diyne bearing methyl and isopropyl groups (43g), a mixture of regioisomers 44g + 44g′ was obtained in high yield with high regioselectivity. For

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• Bruker 400 MHz spectrometer with TMS as an internal standard. Mass spectra were recorded with a Q-TOF mass spectrometer using electrospray positive ionization (ESI+). Enantiomeric ratios were determined by HPLC using a chiral column (Chiralpak AY-H) with hexane/isopropyl alcohol 50:50 as eluents

Coordination-driven self-assembly of discrete Ru₆–Pt₆ prismatic cages

• Aderonke Ajibola Adeyemo and
• Partha Sarathi Mukherjee

Beilstein J. Org. Chem. 2018, 14, 2242–2249, doi:10.3762/bjoc.14.199

• moiety in 3a and 3b were slightly shifted downfield while the isopropyl and methyl protons of the p-cymene moiety in all the cages remained almost unchanged as compared to the arene–ruthenium(II) clips 1a,1b(NO3)2. Additionally, the protons of naphthacenedione in 3a and naphthaquinone in 3b were not

Heterogeneous acidic catalysts for the tetrahydropyranylation of alcohols and phenols in green ethereal solvents

• Ugo Azzena,
• Massimo Carraro,
• Gloria Modugno,
• Luisa Pisano and
• Luigi Urtis

Beilstein J. Org. Chem. 2018, 14, 1655–1659, doi:10.3762/bjoc.14.141

• -isopropyl-5-methylcyclohexanol ((−)-menthol, 1i). The reaction afforded an almost 1:1 mixture of only two diastereoisomers as determined by 1H and 13C NMR analysis of the crude reaction mixture, thus suggesting that it occurs with no epimerization at C1. This result was confirmed by submitting compound 3i

Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119

• was determined by HPLC using a chiral column (Daicel chiral AY-H) with (hexane/isopropyl alcohol 90:10) as eluents, detected at 280 nm. Specific rotations were determined on a Rudolph Research Analytical automatic polarimeter IV. All reactions were monitored by TLC, which were carried out on silica

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• A has shown much higher affinity than parent distamycin A (preferential selectivity towards G·C sites) due to the presence of an isopropyl-substituted thiazole ring, which makes the molecule more hydrophobic [54]. Recently, a small set of analogs of thiazotropsin was designed and synthesized to

• binders [110]. Crystal structure data revealed that nitro groups and ester moieties in conjugates 44 and 45 are coplanar with the pyrrole ring, whereas the isopropyl fragment in conjugate 46 lies out of the pyrrole plane. Coplanarity extends to the second pyrrole ring in case of conjugate 47 and all these

2-Iodo-N-isopropyl-5-methoxybenzamide as a highly reactive and environmentally benign catalyst for alcohol oxidation

• Takayuki Yakura,
• Tomoya Fujiwara,
• Akihiro Yamada and
• Hisanori Nambu

Beilstein J. Org. Chem. 2018, 14, 971–978, doi:10.3762/bjoc.14.82

• to benzophenone in the presence of Oxone® (2KHSO5·KHSO4·K2SO4) as a co-oxidant at room temperature. A study on the substituent effect of the benzene ring of N-isopropyl-2-iodobenzamide on the oxidation revealed that its reactivity increased in the following order of substitution: 5-NO2 < 5-CO2Me, 3

• iodobenzene and 4-iodobenzenesulfonic acid (12) as catalysts [58][59]. As part of our study on the development of multifunctionalized organocatalysts based on hypervalent iodine chemistry [60][61][62][63][64][65][66], we found that N-isopropyl-2-iodobenzamide (13), when utilized as a catalyst with Oxone® at

• of the iodobenzamides depends on the ortho-relationship of the iodine atom to the amide group. Therefore, we then investigated N-isopropyl-2-iodobenzamides that have an additional functional group on the benzene ring. Based on the results of our studies on phenol oxidation [60][62] and Ishihara’s [52

Crystal structure of the inclusion complex of cholesterol in β-cyclodextrin and molecular dynamics studies

• Elias Christoforides,
• Andreas Papaioannou and
• Kostas Bethanis

Beilstein J. Org. Chem. 2018, 14, 838–848, doi:10.3762/bjoc.14.69

• molecule protrudes from the primary rim of host B. The hydrogens of its secondary C24 atom form C–H···O bonds with partially occupied water molecule sites located in the interdimeric space. The isopropyl group of the guest projects through the primary hydroxy rim of host B, clearly higher disordered than

• complex, the bulky cholesterol molecule with a length of about 16.5 Å is encapsulated with its hydroxy group and isopropyl terminal groups protruding from the primary hydroxy rim of the hosts and directly bonded with the hosts of the adjacent complex units, its tight fit in the β-CD dimeric cavity further

• . CHL is found encapsulated axially in a head-to-head β-CD dimer (host A and host B), tightly bound via numerous van der Waals and C–H···O interactions to the inner dimeric host cavity. The hydroxy group and the isopropyl group of the guest protrude from the primary rim of the host A and host B

Chlorination of phenylallene derivatives with 1-chloro-1,2-benziodoxol-3-one: synthesis of vicinal-dichlorides and chlorodienes

• Zhensheng Zhao and
• Graham K. Murphy

Beilstein J. Org. Chem. 2018, 14, 796–802, doi:10.3762/bjoc.14.67

• -dichlorides. Substrates with α-ethyl (2r) and α-isopropyl (2s) substituents reacted similarly, giving chlorinated products in 63–65% yield. Lastly, vinylidene 2t gave chlorodiene 4t as the sole product in 74% yield. As with alkoxy substrate 2m, the α-methylated substrates 2u and 2v possessing methoxy group(s

Biocatalytic synthesis of the Green Note trans-2-hexenal in a continuous-flow microreactor

• Morten M. C. H. van Schie,
• Tiago Pedroso de Almeida,
• Gabriele Laudadio,
• Florian Tieves,
• Elena Fernández-Fueyo,
• Timothy Noël,
• Isabel W. C. E. Arends and
• Frank Hollmann

Beilstein J. Org. Chem. 2018, 14, 697–703, doi:10.3762/bjoc.14.58

• pre-culture to an OD of 0.05 and grown at 37 °C and 180 rpm. At an OD600 of 0.8, 1 mM isopropyl β-D-thiogalactopyranoside (IPTG) was added and the cultures were incubated for additional 4 h at 37 °C and 180 rpm. The bacterial pellets, obtained after harvesting the cells, were re-suspended in a total

Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue

• Romain Sallio,
• Stéphane Lebrun,
• Frédéric Capet,
• Francine Agbossou-Niedercorn,
• Christophe Michon and
• Eric Deniau

Beilstein J. Org. Chem. 2018, 14, 593–602, doi:10.3762/bjoc.14.46

• , substituted at the benzyl para-position by isopropyl and CF3 groups, gave good results with 76 and 74% de (Table 2, entries 9 and 10). Dimeric and trimeric organocatalysts 19 and 20 based on a cinchonine core did not enhance the reaction diastereoselectivity (Table 2, entries 15 and 16). Finally, by