Ru-TsDPEN with formic acid/Hunig's base for asymmetric transfer hydrogenation, a practical synthesis of optically enriched N-propyl pantolactam.

The Noyori-Ikariya catalysts, Ru-TsDPEN 1 or 2, in combination with HCOOH/Hunig's base (5:2) have been successfully utilized for catalytic asymmetric transfer hydrogenation of alpha-ketopantolactam, and optically enriched N-substituted pantolactam was prepared (S/C = 500, up to 95% ee and 99% conversion in HCOOH/Hunig's base condition). More than 2 kg of this key intermediate 9 has been synthesized efficiently with excellent chemical yield and chiral purity.

Indium(III)-catalyzed addition of diethyl acetamidomalonate to terminal alkynes: an efficient approach to beta-branched alpha-amino acids.

The indium(III)-catalyzed Markovnikov addition of active methylene compounds to terminal alkynes has been expanded further to include diethyl acetamidomalonate. This reaction has been studied, and a practical approach to beta-branched alpha-amino acids was developed.

Practical synthesis of 1-aryl-6-(hydroxymethyl)-2-ketopiperazines via a 6-exo amide-epoxide cyclization.

[reaction: see text] Chiral 1-aryl-6-(hydroxymethyl)-2-ketopiperazines can be prepared via an operationally simple, 6-exo epoxide ring-opening cyclization to form the ketopiperazine C6-N1 bond in high yields and with excellent enantiomeric purity.

Further utilization of mucohalic acids: palladium-free, regioselective etherification and amination of alpha,beta-dihalo gamma-methoxycarbonyloxy and gamma-acetoxy butenolides.

Palladium-free etherification and amination of mucohalic acid methyl carbonates 1e (3,4-dichloro-5-methoxycarbonyloxy-5H-furan-2-one) and 1f (3,4-dibromo-5-methoxycarbonyloxy-5H-furan-2-one) and mucochloric acid acetate 1h (3,4-dichloro-5-acetoxy-5H-furan-2-one) was achieved to afford gamma-functionalized alpha,beta-unsaturated gamma-butyrolactones in good to excellent yield. [reaction: see text]

First direct reductive amination of mucochloric acid: a simple and efficient method for preparing highly functionalized alpha,beta-unsaturated gamma-butyrolactams.

[reaction: see text] The first direct reductive amination of mucochloric acid (1) has been accomplished. Reaction of 1 with various alkyl, aryl, and benzylamines, followed by reduction in the same pot, provides an efficient method of obtaining N-benzyl-3,4-dichloro-1,5-dihydro-pyrrol-2-one and N-aryl (or alkyl)-3,4-dichloro-1,5-dihydro-pyrrol-2-ones.

Reinvestigation of mucohalic acids, versatile and useful building blocks for highly functionalized alpha,beta-unsaturated gamma-butyrolactones.

[reaction: see text] Mucohalic acids (mucochloric acid (1, 3,4-dichloro-5-hydroxy-5H-furan-2-one) and mucobromic acid (2, 3,4-dibromo-5-hydroxy-5H-furan-2-one)) are inexpensive, commercially available starting materials with multiple functional groups. These compounds have been modified by way of reduction followed by Suzuki cross-coupling reactions involving arylboronic acids to afford highly functionalized alpha,beta-unsaturated gamma-butyrolactones in excellent yield. The synthetic utility of these building blocks was effectively demonstrated through preparation of the antiinflammatory drug Vioxx.