Reactivity of cyclothiaphosphazenes towards alkyl-lithium reagents

Abstract

Reactions of (NPCl₂)_n(NSOPh)_{3 –n}(n= 1 or 2) with 1 and 2 equivalents of LiMe or LiBu^t and an excess of 2-propanol in tetrahydrofuran lead to complex reaction mixtures, containing the hydridoisopropoxycyclothiaphosphazenes NPH(OPrⁱ)(NPCl₂)_n(NSOPh)_{2 –n}(n= 0 or 1) and several alkyl-substituted ring systems (based on ³¹P and ¹H n.m.r. spectrometry). The structural characterization of the reaction products is described together with the appropriate reaction pathways, based on an initial metal–halogen exchange process. Reactions of the cyclothiaphosphazenes with alkyl-lithium reagents show a tendency to afford lower yields of cyclic derivatives than those previously reported for (NPCl₂)₃. This different behaviour is ascribed to competition between the metal-halogen exchange process and nucleophilic substitution, which is supposed to induce ring cleavage.