P O LIGAND SYSTEMS - SYNTHESIS AND REACTIVITY OF PRIMARY AND SECONDARY O-PHOSPHINOPHENOLS/

Several organometallic reagents such as lithium 2-lithio 4-methylpheno late 1 intermediates formed by orthometallation of o-bromoaryloxy-phos phorus(V)- 2 or -phosphorus(III)-derivatives 3 with magnesium and sodi um, respectively, as well as O-methoxymethyl-protected o-lithio-4-meth ylphenol 4 were used to synthesize suitable precursors 5,6,9,10 of pri mary and secondary o-phosphinophenols. The P-C bond formation involved coupling with ClPR(NMe2), CIPR(O)(OEt) or an intramolecular carbanion ic O --> C shift of the P-substituent. Reduction With LiAlH4, in the c ases of phosphonous or phosphinous acid amides after alcoholysis (to 7 ,8,11), produced primary and secondary o-phosphinophenols 12, respecti vely, or O-protected derivatives 13. o-Phosphinophenols 12 are easily protonated at the phosphorus atom, supported by a P+-H...O hydrogen. b ridge. Metallation (14), acylation, and silylation (16,17) fake place preferably at the hydroxy group and alkylation at the phosphorus atom. Alkylation of 12 and 14 was found to be slow, but C,O-dilithiated spe cies 15 react to give P-secondary (12b,d,e,) or P-tertiary products (2 0,21). Cyclization of 15a with Me2SiCl2 affords the 2,3-dihydro-1,3,2- benzoxaphosphasilol 22, cyclocondensation of 12c with RP(NMe2)(2) or C lP(NMe2)(2) furnishes 2,3-dihydro-1,2,3-benzodiphospholes 23 and 24. A phosphinidenphosphoran 25 is detected in the reaction between 12a and P(NMe2)(3). (C) 1997 John Wiley & Sons, Inc.