Issue Date: October 3, 2011
Silanediols Debut As New Catalyst Class
The hydrogen-bonding abilities of silanediols have been harnessed to activate nitroalkenes toward nucleophilic attack, demonstrating that silanediols are an effective new class of noncovalent, metal-free catalysts (Org. Lett., DOI: 10.1021/ol2021115). Andrew G. Schafer, Joshua M. Wieting, and Anita E. Mattson of Ohio State University note that the ability of silanediols to recognize and bind anions such as acetate and chloride had led chemists to speculate on their potential as hydrogen bond donor catalysts—similar to urea-, thiourea-, and guanidinium-based organocatalysts. But the researchers add that no one followed up to verify those prospects. Mattson’s team jumped in and tried using a naphthyl version (shown) to bind and activate the nitroalkene β-nitrostyrene. The researchers found that the silanediol is proficient at mediating the addition of a range of substituted indoles to variously substituted β-nitrostyrenes. They also explored the potential of chiral silanediols, using a binaphthyl scaffold in place of the naphthyl groups, leading to a racemic catalyst that facilitates addition of 5-methoxyindole to β-nitrostyrene.
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