Further studies of the synthesis of 1-naphthols and 4-hydroxy-5,6-dimethylbenzothiophene by protonation of Cp(CO)2WCTol and Cp(CO)2WC(2-C4H3S) in the presence of alkynes and carbon monoxide

Abstract The previously reported (K.E. Garrett et al., J. Am. Chem. Soc. , 111 (1989) 8383) preparation of a naphthol derivative by protonation of Cp(CO) 2 WCTol in the presence of MeCCMe has been extended to a variety of other alkynes (EtCCEt, HCC n Pr, HCC i Pr, HCC t Bu, MeCC n Pr, MeCC i Pr). Naphthols were produced in each case with the terminal alkynes giving complete regioselectivity for the isomer with the alkyne hydrogen substituent located adjacent to the hydroxy group of the naphthol. This is exactly opposite to the regiochemistry typically observed for Dotz-type benzannulation reactions using (CO) 5 CrC(OR)R′ complexes. Also reported is the crystal structure of the thiophene-substituted carbyne complex Cp(CO) 2 WC(2-C 4 H 3 S) and its reaction with MeCCMe to form 4-hydroxy-5,6-dimethylbenzothiophene.