A theoretical study on the hetero-Diels–Alder reaction of phosphorous substituted diaza- and oxaza-alkenes with olefins derivatives

Abstract

DFT studies indicated that a hetero-Diels–Alder reaction of 4-phosphinyl and 4-phosphonyl-1,2-diaza- and 1,2-oxaza-1,3-butadienes with some olefins take place via an asynchronous concerted mechanism through endo or exo transition states.

Recent Advances in the Chemistry of Conjugated Nitrosoalkenes and Azoalkenes

“…However, the less thermodynamically stable oxazines 60 were readily converted into the more stable 1,2-oxazines 61 in refluxing chloroform via an imine–enamine tautomeric process. The regio- and stereochemistry of the isolated products has been correctly predicted by density functional theory (DFT)-based reactivity indices . Nevertheless, all attempts to prepare 1,2-oxazines bearing a carboxylic acid derivative at C-4 under on-water conditions were unsuccessful.…”

“…The regio-and stereochemistry of the isolated products has been correctly predicted by density functional theory (DFT)-based reactivity indices. 49 Nevertheless, all attempts to prepare 1,2-oxazines bearing a carboxylic acid derivative at C-4 under on-water conditions were unsuccessful.…”

“…However, the cycloaddition of nitrones with an alkyl group instead of a phenyl group was not selective, giving racemic cycloadducts. 49 The asymmetric [4 + 3] cycloaddition of azoalkenes 201 (R 1 = Ph) with azomethine imine 204 gave 1,2,4,5-tetrazepines 205 in high yield with very good enantiomeric excess, by use of the catalytic system Cu(II)/L1. However, racemic cycloadducts were obtained when alkyl-substituted azoalkenes were used.…”

“…The authors observed that the reaction between azoalkenes 201 (R 1 = Me) and nitrones 202 , with the Cu­(I)/ L3 catalytic system, gave 1,2,4,5-oxatriazepanes 203 in good yields with very high enantiomeric excess. However, the cycloaddition of nitrones with an alkyl group instead of a phenyl group was not selective, giving racemic cycloadducts . The asymmetric [4 + 3] cycloaddition of azoalkenes 201 (R 1 = Ph) with azomethine imine 204 gave 1,2,4,5-tetrazepines 205 in high yield with very good enantiomeric excess, by use of the catalytic system Cu­(II)/ L1 .…”