The synthesis of bis- and trisoxazoles via direct arylation is discussed. A variety of aryl groups can be installed at the 2-position of 5-aryl and 5-carboxy-substituted oxazoles under mild conditions using palladium catalysis on water. The direct arylation method can be extended to the synthesis of bis- and trisoxazoles if 2-triisopropylsilyl-4-iodooxazole is used as the electrophile in the arylation.

Alkoxycyclopropanes are readily prepared by reaction of an orthoformate with an alkene in the presence of Me 3 SiCl and zinc.

Conjugate addition of cyanide to chiral a,b-unsaturated oxazolidinones catalyzed by samarium(III) isopropoxide proceeds with good diastereoselectivity. The addition products can be converted into the biologically active targets ent-pregabalin and baclofen.

A synthetic route amenable to large-scale synthesis of the glycine antagonist (2R,4E)-7-chloro-4-(2-oxo-1-phenyl-pyyrrolidin-3-ylidene)-1,2,3,4-tetrahydroquinoline-2-carboxylic acid, (2R,3R,4R,5S)-6-(methylamino)hexane-1,2,3,4,5-penta-ol 12 is presented. The route consists of four stages of chemistry. Stage 1 starts from 5-chloro-2-iodoaniline hydrochloride and is a three-step telescoped stage consisting of an imine formation with ethyl glyoxalate, Mannich reaction using vinyloxytrimethylsilane, and subsequent Wittig reaction with (2-oxo-1-phenyl-3-pyrrolidinyl)triphenylphosphonium bromide. The stage 1 product (4E)-2[(5-chloro-2-iodophenyl)amino]-4-(2-oxo-1-phenyl-pyrrolidin-3-ylidene)butanoic acid ethyl ester 17 is subjected to an enzyme-catalysed kinetic resolution to prepare the single (2R)-enantiomer 19 as the ethyl ester. Stage 3 is the intramolecular Heck reaction to yield (2R,4E)-7-chloro-4-(2-oxo-1-phenyl-pyrrolidin-3-ylidene)-1,2,3,4-tetrahydroquinoline-2-carboxylic acid ethyl ester 31. The final stage is ester saponification and meglumine salt formation to afford the drug candidate molecule 12. In total, more than 300 kg of target 12 was produced with a purity >99.9%. Aspects of route selection as well as elements of process understanding and control are discussed.