Azomethine imines, alkenyl

Azomethine imines can have the alkenyl group attached at carbon, the terminal nitrogen or the internal nitrogen. 

Selectivity in cycloadditions to maleates is mentioned first. The stereoselective cycloadducts produced in maleate cycloadditions are all 2,3-cis-pyrrolidines, indicating that the aryl or 1-alkenyl substituents as R are overlapping with one of the maleate esters in the transition state. More azomethine ylides show high stereoselectivity to dimethyl maleate than to dimethyl fumarate. Thus, there are several azomethine ylide 1,3-dipoles in Table IX that show high stereoselectivity to maleate but poor to fumarate. The N-unsubstituted azomethine ylides RCH=NH —CH COOR, derived from the imines of a-amino esters, are highly endo selective to maleimides, but poor in stereoselectivity to dimethyl maleate on the contrary, the N-substituted derivatives RCH=NR —CH COOR are nonstereoselective to maleimides, but exclusively stereoselective to the maleate. 

A chiral selenophosphoramide catalyst was employed for the intramolecular cyclization of an alkenyl sulfonamide to achieve the enantioselective formation of N-heterocycles including an azepane derivative via a mechanism proposed to include formation of a three-membered sulfur-containing ring (14JA8915). A [4 + 3]-cycloaddition reaction of methyl coumalate 12 with an azomethine ylide, formed from imine esters 13 yielded functionalized azepine derivatives 14 (14OL4508). 

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