ChemInform Abstract: Boron‐Substituted Difluorocyclopropanes: New Building Blocks of gem‐Difluorocyclopropanes.

Abstract

Cyclopropane derivatives Q 0021Boron-Substituted Difluorocyclopropanes: New Building Blocks of gem-Difluorocyclopropanes. -Cycloaddition of difluorocarbene [from (II)] to alkenyl boronates (I) and (XI) provides access towards gem-difluorocyclopropanes in a stereospecific manner. These boronates can be applied to further C-C coupling reactions like homologation [cf. (V)], homologation-oxidation [cf. (VI)], or insertion of synthetically useful structural units [cf. (VIII) and (X)]. -(FUJIOKA, Y.; AMII*, H.; Org. Lett. 10 (2008) 5, 769-772; Dep. Chem., Fac. Sci., Kobe Univ., Nada, Kobe 657, Japan; Eng.) -Mischke 31-072

Enantioselective Rhodium-Catalyzed Hydrogenation of (Z)-N-Sulfonyl-α-dehydroamido Boronic Esters

“…Product 3a was converted successfully to β-amino alcohol 5 with one additional carbon through a homologation/oxidation strategy (Scheme 4b). 30 In addition, the PMB protecting group on the nitrogen of compound 3q was easily removed with trifluoroacetic acid to give 6, which was further transformed to the corresponding potassium trifluoroborate 7 upon treatment with KHF 2 (Scheme 4c). 20 Unfortunately, attempts to deprotect the Ts group in 3a without affecting the boronate functionality were not successful at this moment (see SI).…”