Photochemical cycloaddition of aldehydes to styrenes

Superelectrophilic Fe(III)–Ion Pairs as Stronger Lewis Acid Catalysts for (E)-Selective Intermolecular Carbonyl–Olefin Metathesis

“…This olefin is not observed under the optimal conditions for intermolecular carbonyl–olefin metathesis, which suggests that regioisomeric oxetanes cis - and trans - 8 are not formed as reactive intermediates in this reaction, confirming the lack of observed olefin product 10 . To probe whether the fragmentation of oxetane trans- 9 proceeds stereospecifically (Figure II), oxetane trans - 47 was accessed via Paternò–Büchi reaction protocols as a mixture of isomers (Figure II). trans - 47 , together with oxetane trans - 46 , was characterized as a mixture in a 1:2.6 ratio and subjected to the optimal reaction conditions (Figures II and ).…”

“…The fragmentation of these oxetane intermediates could result in three distinct metathesis products: ( E )- 11 formed upon the fragmentation of trans- 9 , ( Z )- 11 resulting from cis - 9 , and trisubstituted alkene 10 as the product obtained from both cis - and trans - 8 . trans - 46 was synthesized independently via the Paternò–Büchi reaction and subjected to the optimal conditions to gain insight into whether oxetane formation proceeds regioselectively (Figure I). The sole product formed was trisubstituted olefin 23 , which proved stable under reaction conditions.…”

Photochemical Synthesis of Oxetans

“…In the simplest example, benzaldehyde reacts with styrene itself to give cis-and trans-2,3-diphenyloxetan in a 1: 1 ratio (31 % isolated yield). (57) The photocycloaddition of carbonyl compounds to cycloalkenes produces bicyclic oxetans which have proved themselves useful as synthetic intermediates. Often, the nature of the reaction products depends upon alkene concentration.…”

“…( 57) The uv irradiation of methyl pyruvate (MeCOC0 2 Me) and methyl-substituted alkenes in acetonitrile gave oxetans (150/0-54%) as well as allylic ethers and alcohols(58); however, once again, the fully substituted alkene 2,3-dimethylbut-2-ene failed to provide an oxetan (cf. biacetyI048.150»).059) The photoaddition of pyruvamide (MeCOCONHJ to 2,3-dimethylbut-2-ene led only to products of the hydrogen-abstraction type.…”