Addition compounds of n-methyl cyclic imines with trimethylboron,

Abstract

A manometric investigation was made of the addition compounds of trimethylboron with the N-methyl derivatives of ethylenimine (aziridine), trimethylenimine (azetidine), pyrrolidine and piperidine. The stability order obtained was 3->4->5->6-membered ring. This order is different from that reported by and (1) for the trimethylboron addition compounds with the unsubstituted cyclic imines, the order being 4->5->6->3-membered ring. The complete reversal in position of the 3-membered ring upon substituting a methyl group for the hydrogen on the nitrogen in this series is due to large steric interaction. This effect becomes more pronounced as the ring size increases, thereby leading to the systematic decrease in stability. Only in the case of the 3-membered ring does methyl substitution result in a more stable addition compound. For the other ring compounds methyl substitution results in decreased stability, the decrease becoming progressively larger as the ring size increases.