Highly Efficient Peterson Olefination Leading to Unsaturated Selenoamides and Their Characterization

Abstract
The Peterson olefination of aromatic aldehydes with an α-silyl selenoacetamide proceeded smoothly with high stereoselectivity to give E-α,β-unsaturated selenoamides in good to high yields. The reaction with aldehydes bearing alkenyl and dienyl groups gave the corresponding selenoamides bearing dienyl and trienyl groups, but the stability of the products depended on the substituents on the aromatic ring. X-ray molecular analysis disclosed that the α,β,γ,δ-unsaturated selenoamides had a nearly planar structure. In the 77Se NMR spectra, signals were observed in the region greater than 130 ppm depending on the substituents on the aromatic ring, whereas the 1J coupling constant between the carbon atom and the selenium atom was almost independent of the substituents. A linear relationship was observed between the chemical shifts in the 77Se NMR spectra and Hammet σ parameters, and this correlation was retained even when one or two alkenyl groups were introduced to α,β-unsaturated selenoamides, although it became less sensitive.

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