ORGANIC SYNTHESES VIA TRANSITION-METAL COMPLETES .85. [2-(ALKENYLOXY)ETHENYL]CARBENE AND [2-(ARYLOXY)ETHENYL]CARBENE COMPLEXES FROM (1-ALKYNYL)CARBENE COMPLEXES OF CHROMIUM AND TUNGSTEN AND THEIR FRAGMENTATIONTO 2,4-DIEN-5-ONES

[2-(Alkenyloxy)ethenyl]carbene complexes (CO)(5)M=C(OEt)CH=C(O-alkenyl )Ph (3) (M = Cr, W) are obtained by base-catalyzed O-addition of enoli zable 1,3-diones 2 (cyclopentane-1,3-dione and dimedone) to (1-alkynyl )carbene complexes (CO)(5)M=C(OEt)C=CPh (1) (M = Cr, W) together with pyran-2-ylidene complexes 4, which are generated by C-addition of the enolate unit of 2. Thermal fragmentation of the O-addition products 3 affords dienones 5, resulting from overall C-3 insertion of the (1-alk ynyl)carbene ligand of 1 into a C,O bond of 2. Both, O- and C-addition products, 7 and 8, respectively, are derived from reaction of 9-phena nthrol (6) with 1 in a ratio 2:1, but phenol (9a) and 2-naphthol (9b) yield [2-(aryloxy)ethenyl]carbene complexes (CO)(5)M=C(OEt)CH=C(OAr)Ph (10) (M = Cr, W; Ar = Ph, 2-naphthyl) only (81-91%). Addition of 9 is highly regio- and stereoselective and affords stereoisomers (E)-10 in itially, which undergo (E/Z) isomerization in solution to give isomers (Z)-10. Binuclear carbene complexes 12, 14, and 16 CO)(5)M=C(OEt)CH=C (Ph)OArO-(Ph)C=CH(OEt)C=M(CO)(5) (M = Cr, W)] are obtained from dihydr oxyaryl compounds Ar(OH)(2) (Ar = 1,4-phenylene, 1,3-phenylene, 1,1'-b inaphthyl). Addition of cyclohexyl isocyanide (17) to (Z)-10 results i n formation of a ketenmine complex (CO)(5)Cr[CyN=C=C-(OEt)CH=C(OPh)Ph] , which in the presence of water and (excess) 17 affords an (1-amino)= ketocarbene complex (CO)(5)Cr=C(NHCy)C(=O)CH=C(OPh)Ph (18) and an amid e (CyNH)C-(=O)CK(OEt)CH=C(OPh)Ph (19). X-ray data are reported for com pounds (Z)-3b, (E)-10d, and (E,E)-12a.