Stereochemical Control of Reductions. 9. Haptophilicity Studies with 1,1-Disubstituted 2-Methyleneacenaphthenes

• Published in: Journal of organic chemistry 2002-05, Vol.67 (9), p.2813-2825
• Main Authors: Thompson, Hugh W, Rashid, Shaker Y
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed benzenic and aromatic compounds; Exact sciences and technology; Organic chemistry; Preparations and properties
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo010633b

A series of 1-methyl-2-methyleneacenaphthenes has been synthesized, bearing an additional variable substituent (R) at the 1-position. These compounds have been hydrogenated in ethanol over a 5% Pd/C catalyst under standardized conditions in order to assess the haptophilicity of R, its ability to enforce addition of hydrogen from its own face of the molecule by coordination to the catalyst surface. The order of decreasing haptophilicity, assessed as the product epimer ratio, for the groups studied was R = CH2NH2, CH2NMe2, CH2OH, CHNOH, CH2OMe, CHO, CONH2, CH2NHCOMe, COOK, COMe, CN, CONHOH, COOH, COOMe, COONa, COOLi. Because knowledge of group haptophilicities offers potential for stereochemical control in such reductions, comparisons are provided with haptophilic orders found in other molecular systems. It is shown that absolute haptophilicities can be manipulated by varying the dielectric constant of the solvent employed.