Chemoselective Reduction of α,β-Unsaturated Ketones to Allylic Alcohols Under Catalyst-Free Conditions

Chemoselective reductions of α, β-unsaturated ketones to afford the corresponding allylic alcohols have always been challenging. Precious metals and ligands have always been employed in these transformations. Herein, we described...

Oxidative thiocyanation of allylic alcohols: an easy access to allylic thiocyanate within K2S2O8 and NH4SCN

A practical method for the synthesis of allylic thioacyanate from allylic alcohol was disclosed employing K2S2O8 as the oxidant and NH4SCN as the thiocyanate source. Without introducing a leaving group...

Ring-Opening of Epoxides by Pendant Silanols

We present a new ring-opening reaction of epoxides by pendant silanols, catalyzed by either Ph3C+BF4– or BINOL-phosphoric acid. In all cases examined, the reaction is perfectly regioselective and diastereoselective. Silanol epoxides derived from trans-allylic alcohols, cis-allylic alcohols, trans-homoallylic alcohols, and cis-homoallylic alcohols were all compatible and gave products from either endo- or exo-ring opening. With silanol epoxides derived from 4-alkenyl silanols, an unusual rearrangement to tetrahydrofuran products was observed, which is likely the result of tandem nucleophilic attacks. The utility of this methodology was demonstrated in a short preparation of protected D-arabitol.

Highly Efficient Kinetic Resolution of Aryl-Alkenyl Alcohols by Ru-Catalyzed Hydrogen Transfer

No matter through asymmetric reduction of ketones or kinetic resolution of secondary alcohols, enantioselective synthesis of the corresponding secondary alcohols is challenging when the two groups attached to the prochiral or chiral centers are spatially or electronically similar. For examples, dialkyl (sp3 vs. sp3), diaryl (sp2 vs. sp2), and aryl-alkenyl (sp2 vs. sp2) alcohols are difficult to produce with high enantioselectivities. By exploiting our recently developed Ru-catalysts of minimal stereogenicity, we reported herein a highly efficient kinetic resolution of aryl-alkenyl alcohols through hydrogen transfer. This method enabled such versatile chiral building blocks for organic synthesis as allylic alcohols, to be readily accessed with excellent enantiomeric excesses at practically useful conversions.