79288-70-3Relevant academic research and scientific papers
Dipole-Stabilized Carbanions: The α' Lithiation of Piperidides
Beak, Peter,Zajdel, William J.
, p. 1010 - 1018 (2007/10/02)
The α' lithiations and subsequent electrophilic substitutions of two series of piperidides are reported.In the cases of 2,4,6-triisopropylbenzopiperidide (5) and 4-tert-butyl-2,4,6-triisopropylbenzopiperidide (6) lithiations and electrophilic substitutions give α'-substituted products, as shown in Table I, which cannot be cleaved. 2,2-Diethylbutanopiperidide (19), 4-phenyl-2,2-diethylbutanopiperidide (20), and N,N-diethyl-2,2-diethylbutanamide (18) undergo α' lithiation and electrophilic substitution as shown in Table II to give products that can be cleaved to the substituted amines.This sequence thus provides the (α-lithioalkyl)alkylamine synthetic equivalent from secondary amines.The addition of the α'-lithiated piperidides from 20 to aldehydes is shown to provide equatorial substitution with erythro and threo isomers of the amido alcohol 31 produced in a 1:1 ratio.Exclusive conversion to an equatorial threo amino ester 36t is observed on treatment with strong acid.All four possible equatorial-axial and erythro-threo isomers of the amino alcohol 34 can be obtained by appropriate manipulations.The formation of the equatorially substituted products from 6 and 20 and of syn products from N,N-diethyl-2,4,6-triisopropylbenzamide (4) is noted to be consistent with oxygen-lithium complexation and dipole stabilization as important factors in α' lithiation.
Dipole Stabilization of α-Heteroatom Carbanions: Theory and Experiment
Rondan, Nelson G.,Houk, K. N.,Beak, Peter,Zajdel, William J.,Chandrasekhar, Jayaraman,Schleyer, Paul v. R.
, p. 4108 - 4110 (2007/10/02)
The results of ab initio SCF calculations verify dipole stabilization in the carbanions formed by loss of a proton from the methyl groups of methyl formate and N-methylformamide, but differences between theory for the free anions and experiment is attributed to the effect of lithium ion complexation.
