Peter Boehm

Metal-assisted reactions. Part 18. Reaction of titanium tetrachloride with cyclic sulphides: novel bicyclic disulphur compounds

In marked contrast to the reaction of tetrahydrofuran with TiCl4, tetrahydrothiophene did not afford ring-opened products. Instead, small quantities of ring-dimers were produced, possibly via initial chlorination and dehydrochlorination to produce 2,3-dihydrothiophene. An improved synthesis of 2,3-dihydrothiophene is reported.

Metal-assisted reactions. Part 8. Selectivity in the reaction of organic halides with tetrahydroborate and the reduction of acyl halides to aldehydes

Addition of metal ions such as Cu+, Cu2+, Cd2+, and Zn2+ with dimethylformamide to sodium tetrahydroborate in acetonitrile affords a reducing medium in which acyl halides are converted to aldehydes but alkyl, aryl, and benzylic halides are unaffected. The inertness of these last, synthetically useful, functional groups along with the inertness of other potentially reducible groups, makes the reagent very selective for direct reduction of acyl halides to aldehydes. The reducing solution is stable, readily prepared from cheap materials, rapid in action, and easy to use, making the conversion of acids to aldehydes via acyl halides a routine synthetic procedure.