Cu-Catalyzed Double C(sp3)-H Functionalization of Ethylarenes to Form Arylethanolamines.

A double C(sp3)-H functionalization of ethylarenes with alcohols and N-fluorobenzenesulfonimide is reported. The reaction proceeds in three stages. (1) Cu-catalyzed benzylic alkoxylation of ethylarenes gives 1-(1-alkoxyethyl)benzenes. (2) The resulting 1-(1-alkoxyethyl)benzenes are gradually converted into vinylarenes. (3) Cu-catalyzed aminoalkoxylation of the intermediary vinylarenes yields arylethanolamines. Overall, the C-N and C-O bonds are introduced regioselectively at the homobenzylic and benzylic positions of ethylarenes.

Photoassisted Cross-Coupling Reaction of α-Chlorocarbonyl Compounds with Arylboronic Acids.

A Suzuki-Miyaura cross-coupling reaction of α-chloroacetates or α-chloroacetamides with arylboronic acids is made possible by visible-light irradiation. This reaction provides a useful method for the synthesis of α-arylacetates and α-arylacetamides from chlorides under mild reaction conditions. An indole-3-acetic acid derivative that is the key intermediate of the plant hormone auxin can be synthesized from 1-Boc-indole in two steps by combining an iridium-catalyzed C-H borylation and a palladium-catalyzed cross-coupling reaction.

Stereo- and Enantioselective Synthesis of Propionate-Derived Trisubstituted Alkene Motifs.

We report a new method for constructing propionate-derived trisubstituted alkene motifs in a stereoselective manner. 1-Substituted 1,1-di(pinacolatoboryl)-(E)-alk-2-enes are generated in situ from 1-substituted 1,1-di(pinacolatoboryl)alk-3-enes through ruthenium(II)-catalyzed double-bond transposition. These species undergo a chiral phosphoric acid catalyzed allylation reaction of aldehydes to produce the E isomers of anti-homoallylic alcohols. On the other hand, the corresponding Z isomers of anti-homoallylic alcohols are obtained when a dimeric palladium(I) complex is employed as the catalyst for this double-bond transposition. Thus, both E and Z isomers can be synthesized from the same starting materials. A B-C(sp2 ) bond remaining with the allylation product undergoes the Suzuki-Miyaura cross-coupling reaction to furnish a propionate-derived trisubstituted alkene motif in a stereo-defined form. The present method to construct the motifs with (E)- and (Z)-alkenes are successfully applied to the syntheses of (+)-isotrichostatic acid, (-)-isotrichostatin RK, and (+)-trichostatic acid, respectively.

Diastereo- and Enantioselective Synthesis of (E)-δ-Boryl-Substituted anti-Homoallylic Alcohols in Two Steps from Terminal Alkynes.

We report the highly diastereo- and enantioselective preparation of (E)-δ-boryl-substituted anti-homoallylic alcohols in two steps from terminal alkynes. This method consists of a cobalt(II)-catalyzed 1,1-diboration reaction of terminal alkynes with B2 pin2 and a palladium(I)-mediated asymmetric allylation reaction of the resulting 1,1-di(boryl)alk-1-enes with aldehydes in the presence of a chiral phosphoric acid. Propyne, which is produced as the byproduct during petroleum refining, could be used as the starting material to construct homoallylic alcohols that are otherwise difficult to synthesize with high stereocontrol.