ChemInform Abstract: Stereoselectivity of Cycloaddition of N-(Cyanomethyl)- and N-(α-Cyanobenzyl)imines with Olefinic Dipolarophiles.
Abstract
The cyanomethylimine (I) can tautomerize ′to the corresponding N-protonated azomethine ylide which undergoes Cycloaddition with (II) to give - depending on solvent and temp. - either (III) as single stereoisomer or a mixture of (III) and (IV).
ChemInform Abstract
The cyanomethylimine (I) can tautomerize ′to the corresponding N-protonated azomethine ylide which undergoes Cycloaddition with (II) to give - depending on solvent and temp. - either (III) as single stereoisomer or a mixture of (III) and (IV). On heating in xylene, (IV) undergoes slow elimination of HCN to give (V) with retention ofconfiguration, while (III) reacts only in the presence of DBU to give (VI) and (VII). Cycloaddition of (I) with the fumarate (VIII) yields the stereoisomers (IX) and (X), which are converted with loss of HCN into (XI) or (XIII). (XI) is also obtained directly from (I) and the maleate (XII) without stopping at the cycloaddition stage. Various other reactions are described.
