Regiochemistry and stereochemistry of intramolecular [2+2] photocycloaddition of carbon-carbon double bonds to cyclohexenones
摘要:
The intramolecular [2 + 2] photocycloaddition mechanism of alkenes tethered by a three-methylene chain to cyclohexenones has been studied. It was found that the reversion from a 1,4-diradical intermediate to starting material is slow relative to the rate of photoadduct formation. Only ''straight'' closure was observed in the systems studied. For compounds 1-3 and 5, the assumption that the first bond is formed between the beta-carbon of the enone and C-4' leading to a 1,4-diradical is supported. For the formation of compounds 6-11, possible mechanisms are discussed.
Direct Regioselective Dehydrogenation of α‐Substituted Cyclic Ketones
作者:Sebastian Armin Schwengers、Gabriela Guillermina Gerosa、Tynchtyk Amatov、Naoki Yasukawa、Sebastian Brunen、Markus Leutzsch、Benjamin Mitschke、Grigory André Shevchenko、Benjamin List
DOI:10.1002/anie.202307081
日期:2023.8.28
A highly regioselective, one-step dehydrogenation of α-substituted cyclicketones in the presence of 2,3-dichlorobenzo-5,6-dicyano-1,4-benzoquinone is described. The reaction proceeds via phosphoric acid-based enol catalysis and provides access to several α-aryl and α-alkyl substituted α,β-unsaturated ketones.