Photochemie von Aminoketonen. X. Darstellung und diastereoselektive Photocyclisierung von N‐(β‐Benzoylethyl)‐N‐tosyl‐glycinamiden

Photochemistry of Aminoketones. X. Preparation and Diastereoselective Photocyclization of N‐(β‐Benzoylethyl)‐N‐tosyl‐glycinamides The title compounds 4 were prepared by MICHAEL‐like addition of N‐tosylglycinamides to phenyl‐vinyl‐ketone, generated from ω‐bromo‐propiophenone. 300 nm Irradiation of 4a–c (CO–NH) in benzene and acetone, respectively, causes, n, π*‐excitation and photocyclization to (3‐ref‐2‐cis)‐3‐hydroxy‐3‐phenyl‐N‐tosylprolinamides 5. Under the same conditions 4d–h (CONAlk2) yield (3‐ref‐2‐trans)‐prolinamides 6. The difference in diastereoselectivity is explained by intramolecular dipolar interaction in 4* and intramolecular hydrogen bondings in the intermediate hydroxybiradicals.