SYNTHESIS, RESOLUTION, AND DETERMINATION OF ABSOLUTE-CONFIGURATION OFA VAULTED 2,2'-BINAPHTHOL AND A VAULTED 3,3'-BIPHENANTHROL (VAPOL)

Two methods for the synthesis of vaulted biaryls were developed involv ing the reactions of carbene complexes with alkynes and the [2+2] cycl oaddition of ketenes. The final step in the synthesis of 3,3'-diphenyl -[2,2'-binaphthalene]-1,1'-diol (39) and 2,2'-diphenyl-[3,3'-biphenant hrene]-4,4'-diol (47) (VAPOL) was phenol coupling of the 3-phenyl-1-na phthol (14) and the 2-phenyl-4-phenanthrol (28), respectively. The nap hthol 14 could be prepared from the thermolysis of phenylacetyl chlori de in the presence of phenylacetylene or from the benzannulation of th e pentacarbonyl(phenylmethoxymethylene)chromium(0) (15) with phenylace tylene which upon an acetylative workup gives O-acetyl-4-methoxy-2-phe nyl-1-naphthol (16). The reductive cleavage of the acetoxy group in 16 was unexpectedly affected by aluminum chloride and ethanethiol which were used to cleave the methyl ether. In a similar manner, the phenant hrol 28 could either be prepared from the 1-naphthylacetyl chloride (3 0) or tacarbonyl-(1-naphthylmethoxymethylene)chromium(0) (21). A new p rocedure for the preparation of carbene complexes was developed utiliz ing dimethyl sulfate as methylating agent. Unlike the benzannulation o f the phenyl complex 15, the benzannulation of the naphthylcarbene com plex 21 with phenylacetylene gave a side product which resulted from t he incorporation of 2 equiv of the alkyne. This side product could be minimized by the proper control of the concentration of the alkyne. Th e phenol coupling of the 3-phenyl-1-naphthol with ferric chloride gave 2,2'-diphenyl-[2,2'-binaphthalene]-4,4'-diol (38) and with air as oxi dant gave the of 3,3'-diphenyl-[2,2'-binaphthalene]-1,1'-diol (39). Ox idative coupling of the 2-phenyl-4-phenanthrol (28) with air gave 2,2' -diphenyl- [3,3'-biphenanthrene]-4,4'-diol (47) (VAPOL), but the same coupling with 2-tert-butyl-4-phenanthrol (34) failed. The 2,2'-binapht hol 39 was resolved via its cyclic diester with phosphoric acid by sal t formation with (-)-brucine, and the 3,3'-biphenanthrol 47 was resolv ed via its cyclic deiester with phosphoric acid (49) by salt formation with (-)-cinchonidine. The configuration of (-)-39 was shown to be S from an X-ray analysis of the brucine salt, and the configuration of ( +)-47 was shown to be S from an X-ray analysis the amide (S,S)-54 deri ved from 49 and (S)-alpha-methylbenzylamine.