Reactivity of frustrated Lewis pairs with BOC protected diazocarboxylates: FLP capture of diazene.

Abstract

Reactions of (tBuO2CN)2 with FLPs are examined. B(C6F5)3 interacts with the carbonyl oxygen atoms inducing loss of CH2CMe2; however, in the presence of basic donors, the protons are intercepted affording the salts [Hbase]2 [((C6F5)3BO2CN)2] (base = tBu3P 1, NC5H2Ph32, HNC5H6Me43). In contrast, in the presence of (o-Tol)3P, a proton transfers to the diazo-N atom affording (o-Tol)3PN(CO2tBu)NHB(C6F5)34. Further addition of B(C6F5)3 to 4 prompts loss of olefin CH2CMe2 and CO2 affording (o-Tol)3PNHNHB(C6F5)35. The course of these reactions is examined by extensive DFT calculations. The nature of 5 is consistent with the FLP reduction of a diazene fragment.