Stereospecific Photochemical Ring Expansion of Lithiated Benzamides
- 11 July 2003
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 125 (31), 9278-9279
- https://doi.org/10.1021/ja035827i
Abstract
Treatment of N-benzyl benzamides with a strong base (LDA or t-BuLi) followed by irradiation with a 500 W tungsten lamp provides, according to the substitution pattern of the starting amides, either norcaradienes or cycloheptadienones by overall insertion of the N-benzyl group into the benzamide's aromatic ring system. Chiral benzamides undergo the ring expansion with high (sometimes complete) stereospecificity. The reaction appears to occur via a series of pericyclic reactions (photochemical or thermal sigmatropic rearrangements and thermal electrocyclic reactions) following an initial dearomatizing cyclization.Keywords
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