Diastereoselective pentadienylation of chiral α-amino aldehydes was achieved. The obtained anti amino alcohols can be transformed into dienic imines which undergo Diels-Alder cyclisation to give stereoselectively indolizidines.
Various allylstannanes are conveniently prepared in quantitative yields by means of ultrasound-promoted Barbier-type reaction from chlorotributylstannane and allyl halides in a stereoselective manner.
1,2-Naphthoquinone with γ-substituted allyltin reagents undergoes both thermal and photochemical reactions, which show the opposite regioselectivities to each other. The both reactions are supposed to proceed via the initial 1,2-addition, which occurs at the γ-position of the allyltin in the thermal reaction and at the less hindered α-position in the photoreaction, followed by the [3,3] allylic migration.
Simultaneous Control of Regio- and Stereochemistries in the Reaction between α-Alkoxyaldehydes and Pentadienyltin. Selective Preparations of the Four Regio- and Diastereoisomers
作者:Yutaka Nishigaichi、Yasushi Hanano、Akio Takuwa
DOI:10.1246/cl.1998.33
日期:1998.1
In the reaction between α-alkoxyaldehydes and pentadienyltin. each of the possible four regio- and stereoisomers, syn-γ-, anti-γ-, syn-e-, and anti-e-adducts, was selectively synthesized by the use of an appropriate combination of alkoxyl groups, Lewis acids, and solvents applied.
Binary regiocontrolled pentadienylation of imines with a pentadienyltin reagent was achieved. While N-phenyl imines afforded ε-adducts (1,3-dienes) exclusively under Lewis acidic conditions, the combination of N-tosyl imines and indium or zinc chloride as a Lewis acid gave γ-adducts (1,4-dienes) preferentially.