182615-23-2Relevant academic research and scientific papers
Organic syntheses via transition metal complexes. 85. [2-(Alkenyloxy)ethenyl]- and [2-(aryloxy)ethenyl]carbene complexes from (1-alkynyl)carbene complexes of chromium and tungsten and their fragmentation to 2,4-dien-5-ones
Aumann, Rudolf,Fr?hlich, Roland,Kotila, Sirpa
, p. 4842 - 4851 (1996)
[2-(Alkenyloxy)ethenyl]carbene complexes (CO)5M=C(OEt)CH=C(O-alkenyl)Ph (3) (M = Cr, W) are obtained by base-catalyzed O-addition of enolizable 1,3-diones 2 (cyclopentane-1,3-dione and dimedone) to (1-alkynyl)carbene complexes (CO)5M=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 C3 insertion of the (l-alkynyl)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-phenanthrol (6) with 1 in a ratio 2:1, but phenol (9a) and 2-naphthol (9b) yield [2-(aryloxy)-ethenyl]carbene complexes (CO)5M=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 initially, which undergo (E/Z) isomerization in solution to give isomers (Z)-10. Binuclear carbene complexes 12, 14, and 16 [(CO)5M=C(OEt)CH=C(Ph)OArO-(Ph)C=CH(OEt)C=M(CO)5 (M = Cr, W)] are obtained from dihydroxyaryl compounds Ar(OH)2 (Ar = 1,4-phenylene, 1,3-phenylene, 1,1?-binaphthyl). Addition of cyclohexyl isocyanide (17) to (Z)-10 results in formation of a ketenmine complex (CO)5Cr[CyN=C=C-(OEt)CH=C(OPh)Ph], which in the presence of water and (excess) 17 affords an (1-amino)-ketocarbene complex (CO)5Cr=C(NHCy)C(=O)CH=C(OPh)Ph (18) and an amide (CyNH)C-(=O)CH(OEt)CH=C(OPh)Ph (19). X-ray data are reported for compounds (Z)-3b, (E)-10d, and (E,E)- 12a.
