Reaction of Fischer Carbene Complexes with 1,3-Butadiynes:  A New Strategem for Biaryl Synthesis with Construction of the Biaryl Bond Preceding Synthesis of the Arenes

The first examples of the reactions of Fischer carbene complexes with 1,3-butadiynes are reported. These reactions are of interest since they provide new methods for the synthesis of acetylenic substituted arenes and also for the synthesis of biaryls. The reactions of the complexes (CO)5CrC(OR1)R2 [R1 = Me, n-Bu; R2 = phenyl, 1-naphthyl, 1-cyclohexenyl] were investigated with the conjugated diynes R3C⋮CC⋮CR3 [R3 = t-Bu, i-Pr, Ph]. All of the carbene complexes will react with 1 equiv of the diyne to give good yields of acetylenic arenes 5, 19, and 23, each with high selectivity for the regioisomer in which the substituent R3 on the diyne is incorporated adjacent to the phenol function. The reactions of the alkynylarenes 5, 19, and 23 with a second equivalent of carbene complexes, 4, 16, and 22, respectively, generate the bis-phenols 26, 31, and 33, with varying amounts of five-membered-ring annulated compounds as side products. These side products are not seen with the cyclohexenyl complex 22 and can be minimized to some extent for the phenyl complex 4a by proper control of the concentration and the temperature. Attempts to carry out benzannulations of both of the acetylenic functions in the 1,3-diyne concurrently by employing 2 equiv of the carbene complex were not successful, and this is suspected to be due to the presence of a chromium tricarbonyl group on the newly formed arene ring after the first benzannulation, such as in complex 34. The concurrent double benzannulation of a diyne can be achieved in an intramolecular fashion with the bis-carbene complex 39. The intramolecular process leads to a reversal in the regiochemistry of the second benzannulation producing the C 2-symmetrical 2,2‘-binaphthol 40 from the reaction of complex 39 with the diyne 8 along with the indenylnaphthalene 41. The reaction of the optically pure bis-carbene complex 44 derived from (2R,3R)-butane-2,3-diol with diyne 8 gives a single diastereomer of the 2,2‘-binaphthol 46. Chemical correlation with the known 2,2‘-binaphthol 51 reveals that the biaryl axis in 46 has an S-configuration, which was predicted from an examination of models.