A highly regio-and stereoselective selenoxide elimination of 1,2-bis [4-(trimethylsilyl)phenylseleno]alkanes to give (E)-alkenyl selenoxides and its mechanistic studyThe elimination of a 2-substituted selenoxide is known to provide a variety of different products, which are largely dependent on the nature of the substrate and its substituents. Oxidation of (Z)-1,2-bisarylseleno-1-alkenes lead to formation of bisselenoxide intermediate, which gives the corresponding alkynyl selenide by anti-elimination and subsequent reduction by the ArSeOH byproduct. In this study, the selective elimination of selenoxide from 1,2-bis[4-(trimethylsilyl)phenylseleno]alkanes resulted in the exclusive formation of (E)-alkenyl selenoxides via a 1,2-bisselenoxide intermediate. The oxidation of 1,2-bis[4-(trimethylsilyl)phenylseleno]alkanes with one equivalent of metachloroperoxybenzoic acid resulted in the non-selective formation of several arylseleno alkene derivatives, and it was subsequently shown that the elimination of the corresponding 1,2bisselenoxide proceeds with high regio-and stereoselectivity. Mechanistic investigations for this unique elimination have been performed with 77 Se NMR experiments and computational studies.the corresponding allylic product. [3][4][5] The failure of this strategy for the synthesis of enol derivatives from 2-oxygen-substituted selenides has already been reported. This phenomenon was at- [a] A.

A facile and convenient synthesis of trisubstituted (E)-α,β-unsaturated esters was developed by improving our previously established method. The new method circumvented the separation of the intermediates, which have an activating group of the hydroxyl group in β-hydroxy esters, furnishing α,β-unsaturated esters in shorter steps than the previous method: an acetylation of β-hydroxy group and subsequent E1cB reaction proceeded in tandem. In addition, the new method can not only employ a diastereomeric mixture of the substrate for the E1cB reaction, it has a wide substrate scope as well, which would enable the synthesis of various trisubstituted (E)-α,β-unsaturated esters.

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Oxidation of organo‐selenium compounds (I) with MCPBA generates bisselenoxide intermediates which undergo elimination to give products (II) with high regio‐ and E/Z‐selectivity.

Acyclic asymmetric quaternary stereocenters, which are composed of four carbon-carbon bonds, were finely constructed by utilizing a face-selective alkylation of enolate intermediates derived from an asymmetric Michael addition reaction of a chiral lithium amide with trisubstituted (E)-α,β-unsaturated esters. The present face-selective alkylation was able to employ diverse alkyl halides as an electrophile to afford various Michael adducts having an all-carbon quaternary stereocenter. With regard to the deprotection of the chiral auxiliary, N-iodosuccinimide used in our previous study did not work in the present cases; however, we found that pyridine iodine monochloride in the presence of H 2 O was effective to remove the bornyl group and the benzyl group on the amino group to provide the β-amino ester derivative.