A Concise and Atom-Economical Suzuki-Miyaura Coupling Reaction Using Unactivated Trialkyl- and Triarylboranes with Aryl Halides.

A concise and atom-economical Suzuki-Miyaura coupling of trialkyl- and triarylboranes with aryl halides is described. This new protocol represents the first general, practical method that efficiently utilizes peralkyl and peraryl groups of the unactivated trialkyl- and triarylboranes for the Suzuki-Miyaura coupling reaction.

2-deoxyribose as a rich source of chiral 5-carbon building blocks.

We have developed concise routes to a number of useful chiral 5-carbon synthetic building blocks using readily available O-1-methyl-2-deoxyribose as starting material. Novel transformations include the use of indium triflate to catalyze the oxidation of a methyl furanoside to the corresponding lactone with MCPBA and the Vasella-type fragmentation of a 5-iodo furanoside using chromium(II) chloride when zinc proved ineffective. In addition, 3,4-disubstituted piperidine derivatives were prepared without hydroxyl group protection via a simple reductive amination reaction.

One-carbon chain extension of esters to alpha-chloroketones: a safer route without diazomethane.

The reaction of a variety of methyl esters with dimethylsulfoxonium methylide at 0-25 degrees C affords the chain-extended beta-keto dimethylsulfoxonium ylides. Subsequent treatment with hydrogen chloride in THF proceeds with loss of DMSO to afford the corresponding alpha-chloroketones. This sequence has been utilized to convert the methyl esters of CBZ-protected alanine and valine to the anti N-protected alpha-amino epoxides, which are important pharmaceutical intermediates. When the same protocol is applied to BOC-protected phenylalanine methyl ester, epimerization occurs so that the use of a more reactive aryl ester is required. This chemistry provides a practical route to alpha-chloroketones that avoids the use of toxic and explosive diazomethane.