Denis Har

A new, economical, practical and racemization-free method for the reductive removal of 2-oxazolidinones from N-acyloxazolidinones with sodium borohydride

Abstract A new, economical, practical and racemization-free method for the reductive removal of 2-oxazolidinones by a reduction of N-acyloxazolidinones with sodium borohydride in THF and water is described.

A convenient and practical method for N-acylation of 2-oxazolidinone chiral auxiliaries with acids

Abstract A one-pot, convenient and practical method for N-acylation of 2-oxazolidinone chiral auxiliaries directly with acids in the presence of pivaloyl chloride and triethylamine is described.

Double Heck reaction of bridged o, o'-dibromobiaryls with ethyl acrylate

Abstract An inter- followed by an intramolecular double Heck reaction of bridged o,o′-dibromobiaryls with ethyl acrylate is described. The nature of the bridging atom/group determined the outcome of the reaction. This double Heck reaction strategy afforded a safe and convenient synthesis of 9-(ethoxycarbonylmethylene)-9H-xanthene and a novel route to 9 and/or 10-substituted anthracene derivatives.

Enzymatic resolution of (±)-threo-methylphenidate

Abstract The resolution of (±)-threo-methylphenidate by enzymatic hydrolysis with α-chymotrypsin or subtilisin carlsberg to afford (2S,2′S)-(−)-threo and (2R,2′R)-(+)-threo-methylphenidate hydrochlorides in high enantiomeric purities is described.

Using mixed anhydrides from amino acids and isobutyl chloroformate in N-acylations: a case study on the elucidation of mechanism of urethane formation and starting amino acid liberation using carbon dioxide as the probe

Abstract A case study on the elucidation of mechanism of urethane by-product formation and starting amino acid liberation during the conventional two-step isobutyl chloroformate mediated N-acylation is described using carbon dioxide offgas as the probe. The main reason for the urethane formation and starting amino acid liberation was found to be the formation of the symmetrical anhydride of the amino acid during the preparation of the mixed carboxylic–carbonic anhydride intermediate, as determined by quantifying the evolved carbon dioxide. New conditions were developed to minimize this side reaction.

Reaction of benzoyleneurea and isatoic anhydride with the Vilsmeier reagent

Abstract A ring opening and dimerization reaction of benzoyleneurea (1) or isatoic anhydride (2) with thionyl chloride in DMF (Vilsmeier reagent), to yield N,N-dimethyl-2-(4-oxo-3(4H)-quinazolinyl)benzamide (4), is described.

A new, convenient and selective 4-dimethylaminopyridine-catalyzed trifluoroacetylation of anilines with ethyl trifluoroacetate

Abstract A new, convenient, and selective 4-dimethylaminopyridine-catalyzed trifluoroacetylation of anilines with ethyl trifluoroacetate is described. Anilines, containing other functional groups, e.g. alcohols, phenols, hindered secondary amines, and secondary anilines, are also selectively trifluoroacetylated in high yields under these newly developed conditions.

An efficient large scale resolution of (±)-threo-methylphenidate hydrochloride (Ritalin® hydrochloride)

Abstract An efficient and large scale preparation of (2 R ,2′ R )-(+)- threo -methylphenidate hydrochloride ( 3 ) by the resolution of (±)- threo -methylphenidate hydrochloride ( 1 ) salt with O , O ′-dibenzoyl- d -(+)-tartaric acid in the presence of 4-methylmorpholine is described.