Premium
Photochemical Reactions of Regioisomeric 2,2‐Dimethyl‐5,5‐diphenyl‐ and 5,5‐Dimethyl‐2,2‐diphenyl‐Substituted Diazo Ketones of a Tetrahydrofuran Series
Author(s) -
Rodina Ludmila L.,
Malashikhin Sergey A.,
Galkina Olesya S.,
Nikolaev Valerij A.
Publication year - 2009
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200900079
Subject(s) - chemistry , diazo , singlet state , tetrahydrofuran , photodissociation , alkyl , structural isomer , photochemistry , yield (engineering) , aryl , wolff rearrangement , medicinal chemistry , stereochemistry , organic chemistry , excited state , solvent , physics , materials science , nuclear physics , metallurgy
The principal direction of conventional photolysis of the regioisomeric 2,2‐dimethyl‐5,5‐diphenyl‐ and 5,5‐dimethyl‐2,2‐diphenyl‐substituted 4‐diazodihydrofuran‐3(2 H )‐ones 1a and 1b , respectively, is the Wolff rearrangement, while other photochemical processes, which are giving rise to the formation of CH‐insertion, 1,2‐alkyl‐ or ‐aryl‐shifts, as well as H‐atom‐abstraction products occur to a much lower degree ( Schemes 2 and 3 ). The ratio of similar reaction products from both regioisomers 1a and 1b is essentially independent of their structure, and a substantial effect of the relative position of the Ph and diazo group to each other on the yield of CH‐insertion products does not occur. Based on stereochemical considerations, the Wolff rearrangement of diazodihydrofuran‐3(2 H )‐ones apparently proceeds in a concerted manner, whereas the appearance in the reaction mixture of 1,2‐shift and H‐atom‐abstraction products points to the parallel generation during photolysis of singlet and triplet carbenes ( Schemes 4 and 5 ).