Addition products of a P(III)-isothiocyanate to dialkyl acetylenedicarboxylates: A spirocyclic phosphinimine and a triphosphorus heterocycle with tetra- And penta-coordinate phosphorus

Abstract

Treatment of the P(II) isothiocyanate CH2[6-t-Bu-4-Me-C 6H2O]2PNCS (1) with dimethyl acetylenedicarboxylate (DMAD) or diethyl acetylenedicarboxylate (DEAD) yields the spirocyclic phosphinimines CH2[6-t-Bu-4-Me-C6H 2O]2P[NC(S)C(CO2R)C(CO2R)] [R = Me (2), Et (3)], in a reaction unlike those of organic isocyanates. From the reaction of 1 with DEAD, a second product, the triphosphorus compound 5, with the composition [2×1 + 3] but with a completely reorganized structure {CH2[6-t-Bu-4-Me-C6H2O]2P=C(CO 2Et)-C(CO2Et)=CN-}{CH2[6-t-Bu-4-Me-C 6H2O]2P(NCS)}-SC=N-P(S)[(OC6H 2-6-t-Bu-4-Me)2CH2] with tetra- and penta-coordinate phosphorus, is also isolated. Structure and reactivity of these compounds are discussed. Addition of 2,2,2-trifluoroethanol to 2 or 3 leads to the pentacoordinate phosphorus compounds [CH2(6-t-Bu-4-Me-C 6H2O)2- P(OCH2CF3) {C(CO2R)C(CO2R)-C(S)-NH-}] [R = Me (6), Et (7)]. The phosphonate [CH2(6-t-Bu-4-Me-C6H2O) 2P(O)C(CO2Et)=C(CO2Et)-C(S)-NH2] (8) is obtained by evaporating a solution of 7 in open air. © The Royal Society of Chemistry 2005.