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Enantioselective synthesis of biologically active dihydropyrano[2,3‐c]pyrazoles has been achieved through a squaramide‐catalysed Michael addition/Thorpe‐Ziegler type cyclization cascade reaction between arylidenepyrazolones and malononitrile. A series of optically active dihydropyano[2,3‐c]pyrazoles were obtained in excellent yields (up to 99%) and moderate to good enantioselectivities (up to 79% ee) under mild reaction conditions. 相似文献
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An intramolecular, organocatalyzed Michael addition has been developed to obtain biologically important 2,3‐disubstituted cis‐2,3‐dihydrobenzofurans. By using mandelic acid salts of primary aminocatalysts, derived from cinchona alkaloids, the intramolecular cyclization reaction has been developed to proceed in high yield, with moderate to good diastereoselectivity, and up to 99 % ee. Based on the absolute configuration of the formed 2,3‐disubstituted‐cis‐2,3‐dihydrobenzofurans and by considering the observed substrate scope restrictions, a mechanistic rationalization has been presented. 相似文献
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Asymmetric Organocatalyzed Michael Addition of Nitromethane to a 2‐Oxoindoline‐3‐ylidene Acetaldehyde and the Three One‐Pot Sequential Synthesis of (−)‐Horsfiline and (−)‐Coerulescine 下载免费PDF全文
Takasuke Mukaiyama Kento Ogata Prof. Dr. Itaru Sato Prof. Dr. Yujiro Hayashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13583-13588
(?)‐Horsfiline and (?)‐coerulescine were synthesized through three one‐pot operations in 33 and 46 % overall yield, respectively. Key to the success was the efficient use of a diarylprolinol silyl ether to catalyze the asymmetric Michael addition of nitromethane to a 2‐oxoindoline‐3‐ylidene acetaldehyde. This allowed the all‐carbon quaternary, spirocyclic carbon stereocenter to be constructed in good yield with excellent enantioselectivity. 相似文献
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Takahiro Horibe Masato Sakakibara Rin Hiramatsu Kazuki Takeda Kazuaki Ishihara 《Angewandte Chemie (International ed. in English)》2020,59(38):16470-16474
The first one‐pot tandem Michael addition/enantioselective Conia‐ene cyclization of N‐protected prop‐2‐yn‐1‐amines with 2‐methylene‐3‐oxoalkanoates promoted by chiral iron(III)/silver(I) cooperative catalysts has been developed. Alkyl 4‐methylenepyrrolidine‐3‐acyl‐3‐carboxylates, which can be transformed into β‐proline derivatives, are obtained in high yield with high enantioselectivity. 相似文献
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Asymmetric Michael Addition/Intramolecular Cyclization Catalyzed by Bifunctional Tertiary Amine–Squaramides: Construction of Chiral 2‐Amino‐4H‐chromene‐3‐Carbonitrile Derivatives 下载免费PDF全文
The efficient asymmetric Michael addition/intramolecular cyclization of malononitrile with dienones catalyzed by a chiral bifunctional tertiary amine–squaramide catalyst for the synthesis of chiral 2‐amino‐4H‐chromene‐3‐carbonitrile derivatives was developed. The corresponding products were obtained in good to excellent yields (up to 99 %) with excellent enantioselectivities (up to 98 % ee) for most of the bisarylidenecyclopentanones. 相似文献
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Takasuke Mukaiyama Dr. Hayato Ishikawa Dr. Hiroyuki Koshino Prof. Dr. Yujiro Hayashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(52):17789-17800
The one‐pot sequential synthesis of (?)‐oseltamivir has been achieved without evaporation or solvent exchange in 36 % yield over seven reactions. The key step was the asymmetric Michael reaction of pentan‐3‐yloxyacetaldehyde with (Z)‐N‐2‐nitroethenylacetamide, catalyzed by a diphenylprolinol silyl ether. The use of a bulky O‐silyl‐substituted diphenylprolinol catalyst, chlorobenzene as a solvent, and HCO2H as an acid additive, were key to produce the first Michael adduct in both excellent yield and excellent diastereo‐ and enantioselectivity. Investigation into the effect of acid demonstrated that an acid additive accelerates not only the E–Z isomerization of the enamines derived from pentan‐3‐yloxyacetaldehyde with diphenylprolinol silyl ether, but also ring opening of the cyclobutane intermediate and the addition reaction of the enamine to (Z)‐N‐2‐nitroethenylacetamide. The transition‐state model for the Michael reaction of pentan‐3‐yloxyacetaldehyde with (Z)‐N‐2‐nitroethenylacetamide was proposed by consideration of the absolute configuration of the major and minor isomers of the Michael product with the results of the Michael reaction of pentan‐3‐yloxyacetaldehyde with phenylmaleimide and naphthoquinone. 相似文献
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Inside Cover: Asymmetric Organocatalyzed Michael Addition of Nitromethane to a 2‐Oxoindoline‐3‐ylidene Acetaldehyde and the Three One‐Pot Sequential Synthesis of (−)‐Horsfiline and (−)‐Coerulescine (Chem. Eur. J. 42/2014) 下载免费PDF全文
Takasuke Mukaiyama Kento Ogata Prof. Dr. Itaru Sato Prof. Dr. Yujiro Hayashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13410-13410
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Highly Asymmetric Michael Addition to α,β‐Unsaturated Ketones Catalyzed by 9‐Amino‐9‐deoxyepiquinine
Jian‐Wu Xie Wei Chen Rui Li Mi Zeng Wei Du Lei Yue Ying‐Chen Chen Prof. Dr. Yong Wu Prof. Dr. Jin Zhu Prof. Jin‐Gen Deng Prof. Dr. 《Angewandte Chemie (International ed. in English)》2007,46(27):5049-5049
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An efficient enantioselective cascade sulfa‐Michael/Michael addition reaction of trans‐3‐(2‐mercaptophenyl)‐2‐propenoic acid ethyl ester with nitroalkenes catalyzed by a chiral squaramide catalyst was disclosed. This cascade reaction afforded thiochroman derivatives with three contiguous stereocenters in high yields (up to 94%), excellent diastereoselectivities (up to >25:1 dr) and enantioselectivities (up to 99% ee). 相似文献
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Rebekka Anna Bohmann Yuto Unoh Prof. Dr. Masahiro Miura Prof. Dr. Carsten Bolm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(20):6783-6786
A one‐pot Michael addition/cyclization/condensation reaction sequence for the regioselective synthesis of 1,2‐thiazines, starting from propargyl ketones and NH‐sulfoximines or NH‐sulfondiimines, has been developed. Under mild and operationally simple reaction conditions previously unprecedented 1,2‐thiazine 1‐imide and 1‐oxide derivatives are formed in good to excellent yields. The products represent heterocyclic building blocks, readily modifiable by a regioselective C?H bond functionalization, classical cross‐coupling reactions, and deprotection. 相似文献
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Ying‐Fang Ting Chihliang Chang Raju Jannapu Reddy Dr. Dhananjay R. Magar Kwunmin Chen Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(23):7030-7038
Practical and convenient synthetic routes have been developed for the synthesis of a new class of pyrrolidinyl–camphor derivatives ( 7 a–h ). These novel compounds were screened as catalysts for the direct Michael addition of symmetrical α,α‐disubstituted aldehydes to β‐nitroalkenes. When this asymmetric transformation was catalyzed by organocatalyst 7 f , the desired Michael adducts were obtained in high chemical yields, with high to excellent stereoselectivities (up to 98:2 diastereomeric ratio (d.r.) and 99 % enantiomeric excess (ee)). The scope of the catalytic system was expanded to encompass various aldehydes and ketones as the donor sources. The synthetic application was demonstrated by the synthesis of a tetrasubstituted‐cyclohexane derivative from (S)‐citronellal, with high stereoselectivity. 相似文献
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Takashi Tozawa Dr. Hitoshi Nagao Yoshinobu Yamane Teruaki Mukaiyama Prof. Dr. 《化学:亚洲杂志》2007,2(1):123-134
Chiral quaternary ammonium phenoxides were readily prepared from commercially available cinchona alkaloids and proved to be useful new asymmetric organocatalysts. Among various chiral quaternary ammonium phenoxides, a cinchonidine‐derived catalyst that bears both a sterically hindered N1‐9‐anthracenylmethyl group and a strongly electron withdrawing 9‐O‐3,5‐bis(trifluoromethyl)benzyl group were found to be highly effective for the Michael addition of ketene silyl acetals (derived from phenyl carboxylates) and α,β‐unsaturated ketones followed by lactonization. Optically active 3,4‐dihydropyran‐2‐one derivatives were obtained in high yields with excellent control of enantio‐ and diastereoselectivity. This catalyst can be handled in air and stored at room temperature in a sealed bottle without decomposition for at least one month. 相似文献
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One‐Pot Synthesis of Tri‐ and Tetrasubstituted Pyridines by Sequential Ring‐Opening/Cyclization/Oxidation of N‐Arylmethyl 3‐Aziridinylpropiolate Esters 下载免费PDF全文
Prof. Dr. Masahiro Yoshida Tomotaka Mizuguchi Prof. Dr. Kosuke Namba 《Angewandte Chemie (International ed. in English)》2014,53(52):14550-14554
A novel strategy for the one‐pot synthesis of substituted pyridines from N‐arylmethyl 3‐aziridinylpropiolate esters is described. The method employs a three‐step procedure including the formation of allenyl imines, phosphine‐catalyzed cyclization, and subsequent oxidation of the dihydropyridines. Depending on the reaction conditions of the final oxidation step, tri‐ and tetrasubstituted pyridines can be selectively produced. 相似文献