Double Deprotonation of Acetylenic Oxiranes: Synthesis of Allenic Ketones through Dilithio Ynenolates
摘要:
The double deprotonation of acetylenic oxiranes gives allenic ketones through the 1,2-H or 1,2-Ar shift on the transient oxiranyl dianion intermediates. The resulting dilithium ynenolates give allenic ketones upon hydrolysis or can be quenched with various electrophiles.
Metalation of 3-trimethylsilyl propargyl chloride: A stereoselective access to trans-propargylic oxiranes
摘要:
The metalation of 3-trimethylsilyl-1-chloroprop-2-yne and the subsequent reaction with aldehydes affords stereospecifically anti-chlorohydrins which give after treatment with potassium fluoride and NaOH propargylic epoxides with good to excellent yields. (C) 1998 Elsevier Science Ltd. All rights reserved.
Reaction of dialkylzincs with lithiated acetylenic epoxides is described to give zincates that undergo a 1,2-metallate rearrangement by an anti-SN2′ pathway. This rearrangement occurs with the transfer of an alkyl or a silyl group affording allenylzinc intermediates. Allenic and/or homopropargylic alcohols are obtained upon hydrolysis. Quenching the reaction mixture with aldehydes or ketones is shown
描述了二烷基锌与锂化的炔属环氧化物的反应以通过反-S N 2'途径产生经历1,2-金属盐重排的锌酸盐。这种重排通过烷基或甲硅烷基的转移发生而得到烯丙基锌中间体。烯丙和/或均丙醇在水解时获得。显示用醛或酮淬灭反应混合物以立体选择性方式获得2-炔基-1,3-二醇。
Asymmetric Oxidative Lactonization of Enynyl Boronates
We present herein the first oxidation of enynylboronates for the synthesis of γ-lactones, including spiro-, and fused-butanolides as well as butenolides that are prevalent in nature products and bioactive molecules. The asymmetric version of this oxidation was also achieved in the presence of chiral ketone and Oxone. This process successively involves the oxidation of C(sp)−B bond, the epoxidation
The use of alpha-chlorosulfide compounds to control stereoselectivity in indium promoted C-C couplings occurs smoothly at room temperature under aqueous and mixed aqueous/organic conditions. Use of the halide to control syn/anti ratios simplifies the indium promoted coupling with respect to earlier studies and is used to gain entry into stereocontrolled epoxy alkynes in good yields. (C) 1999 Elsevier Science Ltd. All rights reserved.
Metalation of 3-trimethylsilyl propargyl chloride: A stereoselective access to trans-propargylic oxiranes
作者:Fabrice Chemla、Nicolas Bernard、Jean F. Normant
DOI:10.1016/s0040-4039(98)80023-3
日期:1999.1
The metalation of 3-trimethylsilyl-1-chloroprop-2-yne and the subsequent reaction with aldehydes affords stereospecifically anti-chlorohydrins which give after treatment with potassium fluoride and NaOH propargylic epoxides with good to excellent yields. (C) 1998 Elsevier Science Ltd. All rights reserved.
Double Deprotonation of Acetylenic Oxiranes: Synthesis of Allenic Ketones through Dilithio Ynenolates
The double deprotonation of acetylenic oxiranes gives allenic ketones through the 1,2-H or 1,2-Ar shift on the transient oxiranyl dianion intermediates. The resulting dilithium ynenolates give allenic ketones upon hydrolysis or can be quenched with various electrophiles.