The preparation of imidazolidinone and oxazolidinone chelated carbene complexes

The synthesis of several internally chelated imidazolidinone and oxazolidin one Fischer carbene complexes of the type (CO)(4)M = CC(R-1)NCO((CHRCHRX)-C -2-X-3) are reported where the M = chromium, tungsten; R-1 = methyl, ethyl, iso-propyl, phenyl, trans-propenyl, iso-propenyl, iso-butenyl, cyclohexeny l and 1-propynyl; R-2 = H, Ph, Bn, Me, Cy; R-3 = H, Me, Ph; X = O, NMe. Fou r different methods are used for the synthesis of these complexes. The imid azolidinone complexes are best prepared by adding an imidazolidinone or lit hiated imidazolidinone to a methoxy carbene complex or to an in-situ genera ted acetoxy carbene complex. alpha,beta -Unsaturated imidazolidinone comple xes are prepared by aldol condensations of alkyl imidazolidinone complexes or by alkylaltion of these complexes with bromomethyl methyl ether and then elimination of methanol. The oxazolidinone complexes are best made by a tw o-step procedure that involves the addition of an beta -aminoalcohol to a m ethoxy or acetoxy complex followed by closure of the resulting amino carben e complex to the oxazolidinone complex with phosgene. (C) 2001 Published by Elsevier Science B.V.