Organocatalytic Asymmetric Reaction Cascade to Substituted Cyclohexylamines
作者:Jian Zhou、Benjamin List
DOI:10.1021/ja072134j
日期:2007.6.1
We report a new strategy for organocatalytic cascade reactions. Accordingly, enamine catalysis, iminium catalysis, and Bronsted acid catalysis can work in concert in a highlyenantioselective organocatalytic cascadesequence toward chiral cis-3-substituted cyclohexylamines. We found that an achiral amine in combination with a catalytic amount of a chiral Bronsted acid can accomplish an aldol additi
6-aryl-pyrdine-thiosemicarbazones of the formula
where
R1 is hydrogen or methyl;
R2 is (C1-C4)alkyl;
R3 is (C1-C4)alkyl; or
R2 and R3 may be taken together with the nitrogen atom
to which they are attached to form a 3 to 6 membered heterocycle having 2 to 5 nuclear carbon atoms;
X is halo, nitro, (C1-C4)alkyl, (C1-C4)haloalkyl or (C1-C4)alkoxy;
Y is hydrogen, halo, N02, (C1-C4)alkyl or (C1-C4) alkoxy; or when two adjacent positions on the phenyl ring are substituted with alkoxy groups, these alkoxy groups may be joined to form, together with the carbon atoms to which they are attached, a dioxolano or dioxano heterocyclic ring;
n is 0, 1 or 2;
and agronomically acceptable salts thereof are useful as insecticides especially against insects from the order Lepidoptera.
A process for making certain 6-aryl-2-methyl-pyridines, which are useful intermediates in the preparation of biologically active compounds, comprises
(a) subjecting a ketal of 1-hydroxy-1-aryl-5-hexanone to a Jones oxidation to yield a 1-aryl-1,5-hexanedione; or treating the 1-aryl-1-hydroxy-5-ketal-hexane with manganese dioxide in solvent to yield a ketone; and
(b) reacting the 1-aryl-1,5-hexanedione or the ketone from (a) with excess hydroxylamine hydrochloride in polar solvent at a temperature of from 50°C to 100°C.