Mono- and disubstitutions of (hepta-2,5-diyne-1,7-diol) bis(dicobalt) derivatives - Selectivity in Nicholas reactions1

• Published in: Canadian journal of chemistry Vol. 82; no. 2; p. 366
• Main Authors: Guo, Richard, Gibe, Romelo, Green, James R
• Format: Journal Article
• Language: English
• Published: Ottawa Canadian Science Publishing NRC Research Press 01.02.2004
• Subjects: Acids; Chemical bonds; Chemical reactions; Cobalt; Ethers; Ions; MTBE
• ISSN: 0008-4042

Bis(hexacarbonyldicobalt) complexes of benzyl ether - methyl ether or benzyl ether - acetate derivatives of hepta-2,5-diyne-1,7-diols undergo selective Lewis-acid-mediated Nicholas reactions with enol silanes, silyl ketene acetals, and allylstannanes, preferentially replacing the methyl ether or acetate function. Hydride nucleophiles are similarly incorporated selectively using a benzyl ether - alcohol derivative. Subsequent Nichols reaction at the benzyloxy-bearing site may be accomplished with an identical or a different nucleophile, affording skipped 1,4-diyne-Co^sub 4^(CO)^sub 12^ complexes. In instances of lower selectivity for monosubstitution reactions with benzyl ethers, reverting to the use of a menthyl ether - methyl ether complex gives much improved selectivity for methyl ether substitution. [PUBLICATION ABSTRACT] Key words: cobalt alkyne complexes, Nicholas reaction, Lewis acids, 1,4-diynes.