Competing radical, carbanion, and carbene pathways in the reactions of hindered primary alkyl halides with lithium dialkylamides
摘要:
A variety of methods were utilized to study the mechanism of reaction of 6-iodo-5,5-dimethyl-1-hexene and its bromo, chloro, and tosylate derivatives with LDA and several other lithium dialkylamides. In the reaction of 6-iodo-5,5-dimethyl-1-hexene with LDA in THF, radical, carbanion, and carbene pathways occurred simultaneously. However, when the corresponding bromide was allowed to react with LDA, the radical pathway was minor and when the corresponding chloride or tosylate was allowed to react with LDA, no evidence for radical products was observed. This is the first time that competing radical, carbanion, and carbene pathways have been detected in the reaction of a primary alkyl halide with any nucleophile.
An easy synthesis of the 2-phenylsulfonyl-substituted allylic bromides and acetates and their reactivity towards nucleophiles
作者:P. Auvray、P. Knochel、J.F. Normant
DOI:10.1016/s0040-4039(00)85142-4
日期:1986.1
The reaction of phenyl vinyl sulfone with various aldehydes in the presence of a catalytic amount of DABCO furnishes in good yields teh corresponding 2-phenylsulfonyl-substituted alcohols which can be easily converted into their acetates or into their allylicallyrearrangedbromides . These reagents, in turn, react with nucleophides (ketone enolates and cuprates) with an allylicrearrangement (SN2′
The reaction of singletoxygen with cis olefins is regioselective and shows a general preference for hydrogen abstraction on the larger alkyl group of the double bond.
单线态氧与顺式烯烃的反应是区域选择性的,并且在双键的较大烷基上显示出一般优先选择氢。
Reactions of triazolinediones with cis-alkenes. A highly regioselective ene reaction
The enereaction of triazolinedione with unsymmetrical cis-alkenes is regiospecific and shows a preferential abstraction of the allylic hydrogens on the larger alkyl group of the double bond.