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

Copper-catalyzed asymmetric methylation of fluoroalkylated pyruvates with dimethylzinc

• Kohsuke Aikawa,
• Kohei Yabuuchi,
• Kota Torii and
• Koichi Mikami

Beilstein J. Org. Chem. 2018, 14, 576–582, doi:10.3762/bjoc.14.44

• as isopropyl, cyclopentyl, and cyclohexyl led to a higher level of enantioselectivities (90–94% ee), compared to the corresponding ethyl ester 1a. In contrast, trifluoropyruvate 1f with an extremely bulky substituent caused a decrease of enantioselectivity. Ethyl difluoropyruvate (1g) and ethyl

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• espintanol and (±)-schefflone starting from 6-((dibenzylamino)methyl)-3-isopropyl-2,4-dimethoxyphenol. The o-QM formed be trapped by 3-(dimethylamino)-5,5-dimethylcyclohex-2-en-1-one resulting in tetrahydro-1H-xanten-1-one 19 [70]. Starting from phenolic Mannich bases and 3-dimethylamino-2-cyclohexen-1-ones

One-pot sequential synthesis of tetrasubstituted thiophenes via sulfur ylide-like intermediates

• Jun Ki Kim,
• Hwan Jung Lim,
• Kyung Chae Jeong and
• Seong Jun Park

Beilstein J. Org. Chem. 2018, 14, 243–252, doi:10.3762/bjoc.14.16

• thiophenes (8aa–ai) were obtained in moderate to excellent yields (47–92%). When different 1,3-diketones were applied, the yields were affected by the keto–enol tautomer ratio. Alkyl substituents (isopropyl and cyclopropyl), which promote the enol forms of the ketones, afforded thiophenes 8aj and 8ak in good

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• ’ = isopropyl, 42). The reactions were carried out with various metal catalysts in acetic acid and acetonitrile solvents but reactions carried in acetic acid in presence of silica gel impregnated with indium trichloride provided the best results. Júnior et al. [53] also used N,N-dimethylpyrazoylimines 42 with N

Reactivity of bromoselenophenes in palladium-catalyzed direct arylations

• Aymen Skhiri,
• Ridha Ben Salem,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2017, 13, 2862–2868, doi:10.3762/bjoc.13.278

• heteroarenes in the presence of 2 mol % Pd(OAc)2, KOAc as the base in DMA at 90 °C (Scheme 2). The reaction of 2-isopropyl-4-methylthiazole gave the desired product 2 in 82% yield. Conversely, low yields in the target products 3–5 were obtained for the reactions with thiophene-2-carbonitrile, 2-chlorothiophene

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• % yields, respectively. A variety of β-ketoesters and β-ketoamides were tested using the optimized conditions. Alkyl acetoacetates, including pentyl, isopropyl, tert-butyl and methoxyethyl, reacted smoothly with excellent yields (Scheme 2, 3l–3o). β-Ketoamides were well tolerated (Scheme 2, 3h, 3p and 3q

• yields were obtained for β-ketoesters with n-propyl and n-butyl moieties at the C-4 carbon (Scheme 3, 5l and 5m). Bulkier isopropyl and tert-butyl substituents were less well tolerated, with significantly lower yields (Scheme 3, 5n and 5o). The best yield of 99% was obtained when ethyl 4,4,4

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• from the corresponding precursors 17 with methyl, ethyl and isopropyl esters of type E- and Z-1 [19][33][34][35][36]. Remarkably, the reactions of (E)- and (Z)-1b with thiocarbonyl S-methanides 16b-e, in contrast to the corresponding S-isopropanide 16a (Scheme 5), occurred without formation of

Phosphonic acid: preparation and applications

• Charlotte M. Sevrain,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219

• are methyl, ethyl, isopropyl or, occasionally, n-butyl [127]. This observation is likely explained by the synthetic methods employed to prepare phosphonates that frequently made use of the Arbuzov reaction [128] involving the commercially available trimethyl, triethyl or triisopropyl phosphite [129

Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• the reaction mixture. The Gin group established a preactivation glycosylation procedure using glycosyl hemiacetals [36]. As an example, the hemiacetal donor 21 was preactivated with Tf2O and diphenyl sulfoxide (Ph2SO) at −40 °C. This was followed by the addition of the acceptor isopropyl alcohol

Main group mechanochemistry

• Agota A. Gečiauskaitė and
• Felipe García

Beilstein J. Org. Chem. 2017, 13, 2068–2077, doi:10.3762/bjoc.13.204

• adamantoid P4(NR)6 frameworks. These species are synthesised by direct reaction of PCl3 with sterically unhindered amines RNH2 (R= Me, Et, iPr, Bz) [101] or by isomerization of their less thermodynamically-stable macrocyclic [{P(μ-NR)}2(μ-NR)]2 counterparts. In the latter, the isopropyl (iPr) substituted

Selective enzymatic esterification of lignin model compounds in the ball mill

• Ulla Weißbach,
• Saumya Dabral,
• Laure Konnert,
• Carsten Bolm and
• José G. Hernández

Beilstein J. Org. Chem. 2017, 13, 1788–1795, doi:10.3762/bjoc.13.173

• 3). Notably, ethyl acetate (2d), isopropyl acetate (2e) and allyl acetate (2f) were suitable for the enzymatic esterification of erythro-1a as well, although to a lesser extent (Table 2, entries 4–6). Finally, lower and no reactivity was observed using tert-butyl acetate (2g) and acetic acid (2h) as

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Syntheses of 3,4- and 1,4-dihydroquinazolines from 2-aminobenzylamine

• Jimena E. Díaz,
• Silvia Ranieri,
• Nadia Gruber and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2017, 13, 1470–1477, doi:10.3762/bjoc.13.145

• account the boiling points of the alkylating agents and the reactivity of each substrate. As expected, the reaction was selective toward the N-monoalkylation of the arylamino group in the presence of the amide. Satisfactory results were also obtained using the more hindered isopropyl iodide (Table 2

• in precursors 5. The cyclodehydration of acetamides 5a–c proceeded under mild reaction conditions (Table 4, entries 1–3), while acetamide 5d required a higher temperature probably due to the steric hindrance produced by the N-isopropyl moiety (Table 4, entry 4). A higher temperature and a longer

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

Automating multistep flow synthesis: approach and challenges in integrating chemistry, machines and logic

• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2017, 13, 960–987, doi:10.3762/bjoc.13.97

Molecular-level architectural design using benzothiadiazole-based polymers for photovoltaic applications

• Vinila N. Viswanathan,
• Arun D. Rao,
• Upendra K. Pandey,
• Arul Varman Kesavan and
• Praveen C. Ramamurthy

Beilstein J. Org. Chem. 2017, 13, 863–873, doi:10.3762/bjoc.13.87

• substrates (Xinyan Technology Limited, Taiwan) were sequentially cleaned in deionized (DI) water with soap (Hellmanex III), DI water, isopropyl alcohol, acetone and water under sonication for ≈30 min each. The cleaned substrates were then dried with nitrogen gas. UV–ozone was performed on cleaned substrates

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• synthesized a series of novel imidazole-based phosphine ligands, and their effciency was carefully screened [23]. Among these ligands, the one with two isopropyl groups located at the phenyl ring (L3) was effective in converting aryl chlorides and bromides to the corresponding phenols in moderate to excellent

• facilitate C–H hydroxylation of benzoic acids and heteroarenes [55]. An amidation reaction between benzoic acid and 2-(pyridine-2-yl)isopropylamine gave N-(2-(pyridine-2-yl)isopropyl)benzamides, which could be hydroxylated at the ortho position in moderate to excellent yields. The reaction was promoted by a

Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)

• Alexander Bogdanov,
• Cora Hertzer,
• Stefan Kehraus,
• Samuel Nietzer,
• Sven Rohde,
• Peter J. Schupp,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2017, 13, 502–519, doi:10.3762/bjoc.13.50

• attached carbons by a HSQC measurement, and afterwards the fragments of the molecule were elucidated using a COSY experiment. Thus, the COSY data showed correlations of the resonances H3-16, H3-17 and H-1 to H-15, forming an isopropyl moiety. Together with COSY correlations from H-1 over H2-14 to H2-13

Biosynthetic origin of butyrolactol A, an antifungal polyketide produced by a marine-derived Streptomyces

• Enjuro Harunari,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2017, 13, 441–450, doi:10.3762/bjoc.13.47

• system bearing a γ-lactone terminus constitutes the right half of the molecule. To date, no structurally related natural products are known except for its demethyl congener butyrolactol B that was also isolated from the same strain and has an isopropyl group instead of the tert-butyl terminus [9]. Very

• -27). The origin of the tert-butyl group in polyketide biosynthesis is still unknown, however, the tert-butyl functionality of bottromycin and polytheonamide was shown to be produced by radical C-methylation of the isopropyl group of valine [31][32]. By analogy, the tert-butyl portion of 1 was most

• experiments of isotope-labeled precursors in combination with the bioinformatics analysis of its biosynthetic genes. The overall result of labeling experiments is summarized in Figure 8. The tert-butyl group was shown to be derived from the C-methylated isopropyl group of valine. This is the first study that

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• preference for one diastereomer, depending on the substituent R (Scheme 3). With the tert-butyl group in 22a/b a higher selectivity was observed than with the isopropyl group in 21a/b. Still higher discrimination between both diastereomeric faces had been expected using a modified menthol with a phenyl group

• analogous coupling product was obtained with a selectivity of 65% de as well [15]. The selectivity decreases to 38% de for 24a/b with R = isopropyl. When 8-methylmenthol (2) was used, 23a/b was obtained with a moderate selectivity of 27% de, but a good yield of 69%. The facial selectivity for a single

• menthyl 2-tert-butyl and 2-isopropyl-4,4-dimethylpentanoates (21a/b–25a/b) with a chiral centre at C2 of the acid component. For that purpose, malonic half-esters with substituted menthols as chiral auxiliaries were prepared. The half-esters were electrochemically decarboxylated to alkyl radicals. In the

Chromium(II)-catalyzed enantioselective arylation of ketones

• Gang Wang,
• Shutao Sun,
• Ying Mao,
• Zhiyu Xie and
• Lei Liu

Beilstein J. Org. Chem. 2016, 12, 2771–2775, doi:10.3762/bjoc.12.275

• ) was selected as the model reaction for optimization employing Kishi’s oxazoline/sulfonamides as the chiral ligands. A series of oxazoline/sulfonamide ligands (L1–L8) were tested and the results were summarized in Table 1. Four subgroups of R1 were studied (entries 1–4, Table 1) and isopropyl

Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis

• Darcy J. Atkinson,
• Briar J. Naysmith,
• Daniel P. Furkert and
• Margaret A. Brimble

Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226

• addition of sodium iodide to afford the desired cyclic sulfonamide 54. For the synthesis of (±)-enduracididine (1) and (±)-allo-enduracididine (3), protected (±)-allylglycine 55 was treated with BocNHS(O)2NH2, MgO, Rh2(esp)2 and PhI(OAc)2 in isopropyl acetate followed by sodium iodide to afford cyclic

Experimental and theoretical investigations into the stability of cyclic aminals

• Edgar Sawatzky,
• Antonios Drakopoulos,
• Martin Rölz,
• Christoph Sotriffer,
• Bernd Engels and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221

• tetrahydroquinazoline core (Scheme 4b). Thus, anthranilic acid was alkylated by reductive amination with acetone and NaBH4 in two steps to yield the isopropyl-substituted derivative 14. The derivative 14 and the commercially available N-phenylanthranilic acid were converted to amides 15a,b under standard conditions

New furoisocoumarins and isocoumarins from the mangrove endophytic fungus Aspergillus sp. 085242

• Ze’en Xiao,
• Senhua Chen,
• Runlin Cai,
• Shao’e Lin,
• Kui Hong and
• Zhigang She

Beilstein J. Org. Chem. 2016, 12, 2077–2085, doi:10.3762/bjoc.12.196

• the optical rotation of 3 with data reported for dihydrocoumarins [18], it was possible to assign the absolute configuration of C-7 as R. So, the structure of compound 3 was identified as (R)-2-isopropyl-7-methyl-6,7-dihydro-9H-furo[3,2-h]isochromen-9-one. Asperisocoumarin D (4) was isolated as a

• spectrum (Figure 5), allowed the definition of the absolute configuration at C-7 (R) of compound 4 [18]. Thus, the structure of compound 4 was identified as (R)-2-isopropyl-7-methyl-6,7-dihydro-9H-furo[3,2-h]isochromen-9-one. Asperisocoumarin E (5) was obtained as a pale yellow powder and the molecular

• planar structure as (2S,3S,7R)-6,9-dihydro-3-hydroxy-7-methyl-2-(1-methylethyl)-7H-furo[3,2-h][2]benzopyran-9(2H)-one, which was the intermediate of the syntheses of (−)-ustusorane D and (+)-penicisochroman B [8]. Asperisocoumarin C (3) and D (4) had the same structure as (R)-2-isopropyl-7-methyl-6,7