Aldol reaction of 3,3,3-trifluoropropionates

Reported herein is the diastereoselective and enantioselective aldol reaction of 3,3,3-trifluoropropionates. The initial study of enolboration-aldolization of these esters with di-n-butylboron triflate, and dicyclohexylboron triflate is discussed. The development of bis-exo-2-norbornylboron triflate as a reagent for the facile, diastereospecific incorporation of anti-α-trifluoromethyl β-hydroxy moieties is also discussed. The first application of dialkylchloroborane for diastereospecific enolization of 3,3,3-trifuoropropionates has been described. The systematic examination of double diastereoselective aldol reaction of 3,3,3-trifluoropropionates with (+)/(-)-diisopinocampheylboron triflate and (+)/(-)-diisopinocampheylboron chloride is discussed. The development of 2-(arylmethoxy)isopinocampheols as novel chiral auxiliaries and its application for double diastereoselective aldol reaction is also discussed

Ammonia borane-hydrogen cycle: Synthesis, dehydrogenation and regeneration

Herein, we report an optimal procedure for the preparative-scale synthesis of AB in high yields and purity from sodium borohydride and ammonium salts. The first systematic study of the transition metal-catalyzed methanolysis of AB, the isolation and characterization of the resulting borate salt, and recovery of AB has been described. A comparison of the transition metal-catalyzed methanolysis and hydrolysis of AB has been made. We have recognized and quantified the liberation of ammonia during the transition metal-catalyzed hydrolysis. It is known that, borazine, by-product of the pyrolysis reaction, is detrimental to the fuel cell membrane. We have reported an improved procedure for the preparation of borazine and shown that it can also be recycled to ammonia borane via trimethylborate. The solid residue, polyborazylene, formed after pyrolysis of ammonia borane has also been recycled to ammonia borane. Also reported is the direct synthesis of amine boranes form timethyl borate

One-Pot Synthesis of Ammonia–Borane and Trialkylamine–Boranes from Trimethyl Borate

A one-pot procedure for the preparation of ammonia borane from trimethyl borate in 90% yield and >99% purity has been reported. This methodology has been modified to prepare a series of trialkylamine–boranes in 70–82% yields from trimethyl borate and lithium hydride/aluminum chloride in the presence of the corresponding trialkylamine

One-Pot Asymmetric Synthesis of 2- and 2,3-Disubstituted Tetrahydrofuran Derivatives

A novel and convenient one-pot asymmetric synthesis of 2- and 2,3-disubstituted tetrahydrofurans has been achieved in 56–81% yields and 86–99% ee from aliphatic and aromatic aldehydes via an allyl/crotyl/alkoxyallylboration–hydroboration–iodination–cyclization reaction sequence