Sequencing cross-metathesis and non-metathesis reactions to rapidly access building blocks for synthesis
作者:Gopal Sirasani、Tapas Paul、Rodrigo B. Andrade
DOI:10.1016/j.tet.2011.01.080
日期:2011.3
The olefin cross-metathesis reaction has been sequenced with four common organic transformations in a one- or two-pot manner to rapidly access useful building blocks. Those reactions are: (1) phosphorus-based olefination (e.g.. Wittig and Horner-Wadsworth-Emmons); (2) hydride reduction; (3) Evans propionate aldol reaction; (4) Brown allyl- and Roush crotyl-boration. The products of these reactions include stereodefined 2,4-dienoates, trans allylic alcohols, syn-propionate aldols, and chiral non-racemic homoallylic alcohols, respectively. Many of these intermediates have been carried further to natural products, demonstrating the utility of the methodology. (C) 2011 Elsevier Ltd. All rights reserved.
Cycloadditions of highly functionalized C6-synthons to cyclic nitrones
作者:Montserrat Closa、Pedro de March、Marta Figueredo、Josep Font、Angeles Soria
DOI:10.1016/s0040-4020(97)10083-7
日期:1997.12
The 1,3-dipolar cycloaddition of cyclic nitrones to several C6 α,β-unsaturated esters and lactones with different functionalities has been studied. All these olefins have shown high stereoselectivity, with a predominance of the exo or endo transition state for the cis or trans dipolarophiles, respectively. The antifacial approach is favoured in the reactions with γ-substituted hexenolides and also