The methylenation of beta-lactones 5 with dimethyltitanocene provides a versatile, reliable, and highly chemoselective entry to 2-methyleneoxetanes 7. The conversion proceeds selectively in the presence of alkenes, unprotected alcohols, and a variety of other carbonyl moieties, A study of conditions for the optimization of this reaction is delineated. In addition, the first X-ray structure of a 2-methyleneoxetane, which shows its similarity to related p-lactones, is reported. Reactivity studies of 2-methyleneoxetanes are presented in which it is demonstrated that these compounds are attacked at C-4 with a nucleophile; then, subsequently, the resultant enolate reacted with an electrophile. An interesting dichotomy of reactivity was observed when methyleneoxetane 7c was treated with electrophiles. Reaction of 7c with acetic acid gave acetoxyoxetane 19. When 7c was exposed to bromine, dibromoketone 20 resulted.
Studies of the tandem Mukaiyama aldol-lactonization (TMAL) reaction: A concise and highly diastereoselective route to β-lactones applied to the total synthesis of the potent pancreatic lipase inhibitor, (−)-Panclicin D
作者:Hong Woon Yang、Cunxiang Zhao、Daniel Romo
DOI:10.1016/s0040-4020(97)01029-6
日期:1997.12
A concise and highly diastereoselective route to β-lactones has been developed based on a tandemMukaiyamaaldol-lactonization employing thiopyridylsilylketene acetals and various aldehydes. (−)-Panclicin D, a potent pancreatic lipase inhibitor, was synthesized using this methodology. Recent optimization and extensions of this method are described which include variation of the silyl group and leaving
Carbonylation of <i>cis</i>-Disubstituted Epoxides to <i>trans</i>-β-Lactones: Catalysts Displaying Steric and Contrasteric Regioselectivity
作者:Michael Mulzer、Geoffrey W. Coates
DOI:10.1021/jo501899e
日期:2014.12.19
trans-beta-Lactones are a versatile and useful class of compounds, but reliable methods for their direct synthesis are still limited. Addressing this problem, we present herein two catalysts for the regioselective carbonylation of cis-disubstituted epoxides. The two catalysts show high activities and opposing regioselectivities so that either one of the two possible beta-lactone regioisomers can be obtained selectively.
A Highly Diastereoselective, Tandem Mukaiyama Aldol-Lactonization Route to β-Lactones: Application to a Concise Synthesis of the Potent Pancreatic Lipase Inhibitor, (−)-Panclicin D
作者:Hong Woon Yang、Daniel Romo
DOI:10.1021/jo9619488
日期:1997.1.1
Preparation and Properties of 2-Methyleneoxetanes
作者:Lisa M. Dollinger、Albert J. Ndakala、Mehrnoosh Hashemzadeh、Gan Wang、Ying Wang、Isamir Martinez、Joel T. Arcari、David J. Galluzzo、Amy R. Howell、Arnold L. Rheingold、Joshua S. Figuero
DOI:10.1021/jo9906072
日期:1999.9.1
The methylenation of beta-lactones 5 with dimethyltitanocene provides a versatile, reliable, and highly chemoselective entry to 2-methyleneoxetanes 7. The conversion proceeds selectively in the presence of alkenes, unprotected alcohols, and a variety of other carbonyl moieties, A study of conditions for the optimization of this reaction is delineated. In addition, the first X-ray structure of a 2-methyleneoxetane, which shows its similarity to related p-lactones, is reported. Reactivity studies of 2-methyleneoxetanes are presented in which it is demonstrated that these compounds are attacked at C-4 with a nucleophile; then, subsequently, the resultant enolate reacted with an electrophile. An interesting dichotomy of reactivity was observed when methyleneoxetane 7c was treated with electrophiles. Reaction of 7c with acetic acid gave acetoxyoxetane 19. When 7c was exposed to bromine, dibromoketone 20 resulted.