Chelation-assisted regioselective C-O bond cleavage reactions of acetals by Grignard reagents. A general procedure for the regioselective synthesis of protected polyols having one free hydroxy group

Wen Lung Cheng, Yeng Jeng Shaw, Sue Min Yeh, Puthuparampil P. Kanakamma, Yu Huey Chen, Chuo Chen, Jia Cheng Shieu, Shaang Jyh Yiin, Gene Hsiang Lee, Yu Wang, Tien Yau Luh

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11 Scopus citations

Abstract

Acetals containing a neighboring heteroatom react with the Grignard reagent in aromatic hydrocarbon solvents regioselectively. The auxiliary moiety can be hydroxy, alkoxy, or amino but not sulfur. Chelation plays a key role in directing the regioselectivity of this ring opening reaction. The reactions of acetonide derivatives of monosaccharides under these conditions afford the corresponding products having only one free hydroxy group at the specific position. Fully protected mannosamine derivative is prepared in good yield. The stereochemistry of the carbon center where auxiliary group is attached can be either syn or anti to the acetal oxygen moiety where cleavage of the C-O bond occurs. However, difference in reactivity has been found in the reaction of tris-acetonide of sorbitol with MeMgI. Regioselective ring opening of the acetal group at the anomeric carbon generates a hemiacetal which underwent further nucleophilic addition to furnish the corresponding alcohol stereoselectively.

Original languageEnglish (US)
Pages (from-to)532-539
Number of pages8
JournalJournal of Organic Chemistry
Volume64
Issue number2
DOIs
StatePublished - Jan 22 1999

ASJC Scopus subject areas

  • Organic Chemistry

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