Highly efficient synthesis of alka-1,3-dien-2-yltitanium compounds from alka-2,3-dienyl carbonates. A new, practical synthesis of 1,3-dienes and 2-iodo-1,3-dienes
摘要:
Treatment of carbonates of alka-2,3-dien-1-ols 2 with (eta(2)-propene)Ti(O-i-Pr)(2) (I) resulted in oxidative addition to afford 1,3-dien-2-yltitanium compounds 3, which react readily with electrophiles such as H+, I-2 and aldehydes. The reaction with H+ and I-2 proceeds highly regioselectively, thus providing an efficient and practical method for synthesis of 1,3-dienes and 2-iodo-1,3-dienes. Copyright (C) 1996 Elsevier Science Ltd.
Tungsten-Promoted Intramolecular Alkoxycarbonylation for Synthesis of Complex Oxygenated Molecules
作者:Chi-Chung Chen、Jang-Shyang Fan、Su-Ju Shieh、Gene-Hsian Lee、Shie-Ming Peng、Sue-Lang Wang、Rai-Shung Liu
DOI:10.1021/ja9617808
日期:1996.1.1
Intramolecular alkoxycarbonylation of tungsten-propargyl compounds proceeds with excellent diastereoselectivities to form eta(3)-delta- and -epsilon-lactones but for gamma-lactones. With OSi(t-Bu)Me(2) substituted for an or-hydroxy group, eta(3)-gamma-lactones are stereoselectively formed with syn stereoselection. An optically active tungsten eta(3)-gamma-lactone is prepared from D-(+)-xylose to illustrate the stereochemical effect of OSi(t-Bu)Me(2). All these eta(3)-gamma-, -delta-, and -epsilon-lactones are converted to allyl anions that react in situ with aldehydes and ketones to produce various beta-(hydroxylalkyl)-alpha-methylene-gamma-lactones with good diastereoselectivity. This reaction is also applied to the synthesis of chiral alpha-methylene butyrolactones. Organic carbonyls add to the pi-allyl groups of eta(3)-gamma- and -delta-lactones opposite the tungsten fragment, whereas additions occur from the metal side for eta(3)-epsilon-lactones. The stereochemical courses of these reactions are discussed in detail. These two tungsten-promoted reactions efficiently effect stereoselective transformation of chloroalkynols to complex alpha-methylene-gamma-lactones, which are useful materials for syntheses of trisubstituted 1,3-, 1,4-, and 1-5-diols.
Highly efficient synthesis of alka-1,3-dien-2-yltitanium compounds from alka-2,3-dienyl carbonates. A new, practical synthesis of 1,3-dienes and 2-iodo-1,3-dienes
作者:Sentaro Okamoto、Hiroyoshi Sato、Fumie Sato
DOI:10.1016/s0040-4039(96)02126-0
日期:1996.12
Treatment of carbonates of alka-2,3-dien-1-ols 2 with (eta(2)-propene)Ti(O-i-Pr)(2) (I) resulted in oxidative addition to afford 1,3-dien-2-yltitanium compounds 3, which react readily with electrophiles such as H+, I-2 and aldehydes. The reaction with H+ and I-2 proceeds highly regioselectively, thus providing an efficient and practical method for synthesis of 1,3-dienes and 2-iodo-1,3-dienes. Copyright (C) 1996 Elsevier Science Ltd.
An Efficient CuCN-Catalyzed Synthesis of Optically Active 2,3-Allenols from Optically Active 1-Substituted 4-Chloro-2-butyn-1-ols
作者:Jing Li、Wangqing Kong、Chunling Fu、Shengming Ma
DOI:10.1021/jo900710e
日期:2009.7.17
The sequential treatment of opticallyactive terminal propargylic alcohols with n-BuLi/(HCHO)n and regioselective chlorination afforded the corresponding opticallyactive 4-chloro-2-butyn-1-ols. With R1 being a methyl or an ethyl group, an alternative for the synthesis of the corresponding opticallyactive propargylic alcohols is the Novozym 435-catalyzed kinetic resolution of these racemic 4-chloro-2-butyn-1-ols