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

• Published in: Canadian journal of chemistry Vol. 82; no. 2; pp. 366 - 374
• Main Authors: Guo, Richard, Gibe, Romelo, Green, James R
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.02.2004; CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS
• Subjects: Chemistry; Chemistry, Multidisciplinary; Physical Sciences; Science & Technology; PAUSON-KHAND REACTION; Lewis acids; cobalt alkyne complexes; CATIONS; 1,4-diynes; POLYACETYLENES; ALKYNE COMPLEXES; Nicholas reaction; HYDROGEN-BOND BASICITY; COBALT COMPLEXES; PROPARGYLIC ALCOHOLS; SPONGE PETROSIA SP; STEREOSELECTIVE-SYNTHESIS; BIS(PROPARGYLDICOBALT) DICATION EQUIVALENTS
• ISSN: 0008-4042; 1480-3291
• DOI: 10.1139/v03-209

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 Nicholas reaction at the benzyloxy-bearing site may be accomplished with an identical or a different nucleophile, affording skipped 1,4-diyne-Co 4 (CO) 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.Key words: cobalt alkyne complexes, Nicholas reaction, Lewis acids, 1,4-diynes.