Reactions of Trialkylamines with the Cyclocarbaphosphazene Cl2PN(ClCN)2: Selectivity in the Cleavage of Alkyl Groups

Abstract

Reactions of unsymmetrically substituted trialkylamines MeNEt 2 , MeN(allyl) 2 , MeN(Benzyl) 2 , Me 2 N(Benzyl), EtNPr i 2 , MeNPr i 2 , MeN(c-C 6 H 11 ) 2 , and Me 2 N(c-C 6 H 11 ) with the carbaphosphazene (ClCN) 2 (Cl 2 PN) were carried out to understand the preference for the cleavage of various alkyl groups on the amino nitrogen. All the trialkylamines underwent dealkylation and the generated dialkylamino groups substituted regiospecifically on the carbon atoms of the cyclocarbaphosphazene. When MeNEt 2 was reacted with (ClCN) 2 (Cl 2 PN), one of its ethyl groups was preferentially cleaved. Deallylation was favored over the cleavage of methyl group in the reaction of MeN(allyl) 2 with (ClCN) 2 (Cl 2 PN). Benzyl and cyclohexyl groups were more readily cleaved than the methyl group when MeN(Benzyl) 2 , Me 2 N(Benzyl), MeN(c-C 6 H 11 ) 2 , and Me 2 N(c-C 6 H 11 ) were reacted with (ClCN) 2 (Cl 2 PN). The isopropyl group was found to be cleaved preferentially over ethyl and methyl groups in the reactions of EtNPr i 2 and MeNPr i 2 with (ClCN) 2 (Cl 2 PN). Sterically hindered trialkylamines also underwent dealkylation with monosubstitution of the carbaphosphazene. The results show that the ease of cleavage of the alkyl groups depends primarily on the stability of the alkyl carbocation of the cleaved group.