Enantioselectivity in the allylboration of N-silylimines with a variety of chirallymodifiedallylboronreagents has been examined. Optically active N-sulfonylamino alcohols (16, 17 and 19) derived from D-camphor and norephedrine were found to be efficient chiral ligands for the allylboration reagent. These reagents smoothly reacted with N-silylimines to give the corresponding homoallylic amines in
readily available from iminoether hydrochlorides and acid chlorides. According to a more general route towards these doubly activated dienes, N-trialkylsilylimidates and N-trialkylsilylimines derived from non-enolizable aldehydes were conveniently converted in a one-pot sequence into the corresponding azadienes by reaction with an acid chloride in the presence of triethylamine. Finally, cyclic dienes could
已经通过三种途径制备了在C-3处带有活化三烷基甲硅烷基氧基的2-Aza-1,3-二烯。第一条途径涉及N-酰基酰亚胺的甲硅烷基化,其可从亚氨基醚盐酸盐和酰氯容易获得。根据朝向这些双活化二烯的更通用的途径,通过在三乙胺的存在下与酰氯反应,将由不可烯化的醛衍生的N-三烷基甲硅烷基酰亚胺酯和N-三烷基甲硅烷基亚胺方便地以一锅法转化为相应的氮杂二烯。最后,可以通过在三乙胺的存在下用三烷基甲硅烷基三氟甲磺酸酯在两个氧上将戊二酰亚胺直接甲硅烷基化来制备环状二烯。2-氮二烯的构型和构象已由1 H,13确定C和15 N NMR光谱。
COLVIN, ERNEST W.;MCGARRY, DANIEL;NUGENT, MARK J., TETRAHEDRON, 44,(1988) N 13, 4157-4172
作者:COLVIN, ERNEST W.、MCGARRY, DANIEL、NUGENT, MARK J.
DOI:——
日期:——
Silicon-assisted synthesis of β-lactams
作者:Ernest W. Colvin、Daniel McGarry、Mark J. Nugent
DOI:10.1016/s0040-4020(01)86663-1
日期:1988.1
Reaction of -silyl imines with silyi keteneacetals in the presence of ZnI2 and t-butyl alcohol, followed by treatment of the intermediate -silyl β-aminoesters with MeMgBr, produces -silyl-azetidin-2-ones in good yield; use of trimethylsilyl triflate as Lewis acid catalyst can be advantageous in some cases. The preparation of the -t-butyldimethylsilyl imine of ethyl glyoxylate in this context is detailed
A new and efficient synthesis of N-(TIPS)imines and N-(TBDMS)-imines starting from enolizable and non-enolizable aldehydes is described. We tested the reactivity of these imines in the preparation of β-lactams. N-(TBDMS)imines effectively give N(-TBDMS)azetidinones with a trans stereochemistry of the ring substituents, complementing N-(TMS)imines which instead afford cis β-lactams. In contrast, N-(TIPS)imines react with ester enolates in few cases because of the extremely low rate of the ring-closure step, so that a decomposition of enolates occurred.