Carbon Homologation of 1-Alkynes Using Alkoxymethyl Esters Mediated by Dichlorobis(trichloromethanesulfonato)titanium(IV)

Article abstract of DOI:10.1246/bcsj.67.3309

Various 1-alkynes were converted to 1-alkoxy-3-chloro-2-alkenes using alkoxymethyl esters and dichlorobis(trifluoromethanesulfonato)titanium(IV) . This carbon homologation proceeded in the case of not only simple 1-alkynes but also for several 3- or 4-dimethylcarbamoyloxy-, 5-benzoyloxy-, 5-phenoxycarbonyloxy-, and 5-methoxycarbonyloxy-1-alkynes. Among them, 3- and 4-dimethylcarbamoyloxy-1-butynes underwent the reaction without loss of their functionalities compared with the other oxy substrates. The stereoselectivity was Z predominant, especially in the case of the above mentioned 3-, 4-, and 5-oxy substituted 1-alkynes. Addition of TiCl4 to this system was somewhat effective for enhancing the Z ratios. Titanium(IV) bis(triflate) was the only effective catalyst among several Lewis acids such as AlCl3, TiCl4, SnCl4, ZnCl2, and Sn(OTf)2. As a functionalization of the obtained vinyl chloride, 3-chloro-4-dimethylcarbamoyloxy-1-methoxy-2-pentene was converted into the corresponding ketone using Hg(OCOCF3)2.