Lead Tetraacetate Cleavage of Chiral Phenylglycinol Derived Secondary Amines Without Racemization
摘要:
Diastereomerically enriched N-(1,1-disubstituted methyl)(2-hydroxy-1'-phenylethyl)amines were oxidatively converted to enantiomerically enriched primary disubstituted methylamines in excellent yields without racemization, using an improved lead tetraacetate (LTA) procedure.
Factors influencing the stereoselectivity in the cycloaddition of imino-dienophiles derived from amino ethers, amino alcohols, and amino acid esters
作者:Paul N. Devine、Michael Reilly、Taeboem Oh
DOI:10.1016/s0040-4039(00)73790-7
日期:1993.9
Imino dienophiles derivedfrom amino ethers, amino alcohols and amino esters undergo Lewis acid promoted cycloaddition with Danishefsky's diene. Cyclic chelation between the imine and oxygen atom increases the stereoselectivity of the reaction.
The diastereoselectivenucleophilicaddition of alkyllithium to N-alkylidene-alpha-naphthylethylamine was carried out. In the presence of Lewis acids or Lewis bases, organolithiums reacted smoothly with imines to give the corresponding amines in high stereoselectivity (up to 100% de). Furthermore, the resulting opticallyactive amines were found to be useful for asymmetric reactions as chiral ligands
Barbier-type allylation of unactivated aldimines with allyl bromides in the presence of indium powder took place rapidly in alcoholic solvents to give homoallylic amines in fair to good yields.
[reaction: see text] The first successful catalytic oxidation procedure for the chemoselective conversion of imines to nitrones is reported. The reaction is general, high yielding, and user and environmentally friendly, and furnishes a solution to the yet unanswered issue of regioselective access to nitrones by oxidation of nitrogen derivatives.
Chiral aldimines derived from phenylglycinol were diastereoselectively allylated with indium powder/allyl bromide in alcoholic solvents. Both aliphatic and aromatic aldimines provided good yield of the desired products with high diastereoselectivity. A racemization-free protocol for removal of the phenylglycinol auxiliary was also developed. The stereochemical assignment of the homoallylic amine was