Diastereoselective Paterno-Buchi reaction on furan derivatives-reaction with asymmetric ketones

The photochemical reaction of 1-phenyl-2-methyl-1-butanone with furan gave propiophenone via a Norrish Type II reaction. The same behavior was observed using 1-phenyl-2-methyl-1-pentanone. In this case, the product derived from a Norrish-Yang reaction was obtained. The photochemical reaction of 2-phenylpropiophenone with furan and 2-methylfuran gave the corresponding Paterno-Buchi adducts. 2-Methylfuran gave a mixture of regioisomers. All the products of the Paterno-Buchi reaction were obtained with >98% de. The diastereoselectivity was explained by considering the relative stability of the biradical intermediates.