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Review | Regular issue | Vol 83, No. 3, 2011, pp.447-489
Published online, 11th January, 2011
DOI: 10.3987/REV-10-682
■ Tandem Reactions Initiated by the Conjugate Addition of Chalcogen Compounds ― Utilization and Synthesis of Heterocycles ―

Tadashi Kataoka and Shin-ichi Watanabe*

*College of Pharmacy, Kinjo Gakuin University, 2-1723 Omori, Moriyama-ku, Nagoya 463-8521, Japan

Abstract

Alkynyl- and alkenylselenonium salts reacted with nucleophiles at the α- or β-carbon depending upon the nucleophiles. The α-attack caused the addition-elimination reaction; i.e., the apparent substitution reaction and the β-attack (the conjugate addition) generated an ylide, which brought about the tandem reaction to form a variety of heterocyclic compounds. Some new reactions proceeded via the selenuranes formed by the attack of a nucleophile on the positively charged selenium atom.
An interesting tandem Michael-aldol reaction of enones (ynones) bearing a chalcogenide or a thioamide was developed. The reactions of the 1-[2-(methylchalcogeno)phenyl]propenones gave α-(α-hydroxyalkyl)enones (Morita-Baylis-Hillman adducts) after a work-up with Et3N. The reactions of the 3-cinnamoyl-1,3-oxazolidine-2-thiones with aldehydes gave tricyclic compounds with a bridgehead bound to four heteroatoms. The asymmetric reactions simultaneously induced four stereocenters, three of which are contiguous. Removal of the chiral auxiliary provided 1,3-diols bearing three consecutive stereocenters.