作者:Diego J. Ramon、Miguel Yus
DOI:10.1021/jo00012a012
日期:1991.6
The lithiation of the chloro ketals 9 with lithium naphthalenide at -78-degrees-C led to the corresponding masked lithium bishomoenolates 4, which are stable species under these conditions and react with different electrophilic reagents (H2O, D2O, i-PrCHO, PhCHO, MeCOEt, (activated CH2)4CO, (activated CH2)5CO, (activated CH2)7CO, PhCOMe, c-C3H5COPh, PhCN, HCONMe2, PrCO activated N(CH2)4, PhCO activated N(CH2)4, PhCOCl, EtOCOCl, PhCHNPh, and (PhCH2S)2) to give, after hydrolysis with water, the corresponding bifunctionalized compounds 10a-22a, 10b-22b, and 10c-15c. When alkyl halides were used as electrophiles the reaction failed. In the presence of a catalytic amount of the complex CuBr.Me2S, the same reaction with alpha,beta-unsaturated ketones (methyl vinyl ketone or 2-cyclohexanone) yielded the expected products of a 1,4-addition 25a-c and 26b. The deprotection of the masked carbonyl group was easily done by treatment with 2 N hydrochloric acid in THF, so as examples, compounds 27a-29a, 30b, 31b, 32c, and 33c were isolated. The transformation of hemiacetals of the type 27a into substituted tetrahydropyrans was carried out by means of compounds of the type R3SiNu (Nu = H, allyl, CN) in the presence of BF3, so products 34a-41a, 42b, and 43b were prepared. Finally, the in situ oxidation of the deprotected products of the type 27a-arising from the reaction of bishomoenolate 4a with carbonyl compounds-with Jones reagent (for ketones derivatives) or PCC (for aldehydes derivatives) led to the corresponding delta-lactones 44-57.