Novel reactions of phosphorus(iii) azides and isocyanates: unusual modes of cycloaddition with dipolarophiles and an unexpected case of ring expansion†
Abstract
New modes of 1,3-dipolar cycloaddition are uncovered by the isolation of [CH2(6-t-Bu-4-Me-C6H2O)2]P{C(CO2Me)C(CO2Me)N[NP(N3)(OC6H2-6-t-Bu-4-Me)2CH2]N} (3) and [CH2(6-t-Bu-4-Me-C6H2O)2]P{C(CO2Me)C(CO2Me)C(O)N} (4) on treating [CH2(6-t-Bu-4-Me-C6H2O)2]P-X [X = N3 (1) and NCO (2)] with the dipolarophile MeO2CCCCO2Me; compound 4 undergoes an unprecedented ring expansion upon addition of 2-(methylamino)ethanol to afford the spirocycle [CH2(6-t-Bu-4-Me-C6H2O)2]P{OCH2CH2N(Me)CH(CO2Me)CH(CO2Me)C(O)N} (5).