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Diastereomeric Discrimination in the Lifetimes of Norrish Type II Triplet 1,4‐Biradicals and Stereocontrolled Partitioning of Their Reactivity (Yang Cyclization versus Type II Fragmentation)
Author(s) -
Moorthy Jarugu Narasimha,
Koner Apurba L.,
Samanta Subhas,
Singhal Nidhi,
Nau Werner M.,
Weiss Richard G.
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600880
Subject(s) - diastereomer , chemistry , fragmentation (computing) , flash photolysis , radical , reactivity (psychology) , photochemistry , reaction rate constant , stereochemistry , organic chemistry , kinetics , physics , medicine , alternative medicine , pathology , quantum mechanics , computer science , operating system
The stereochemistry at C2 and C3 carbons controls the partitioning of triplet 1,4‐biradicals of ketones 2 among various pathways. Differences in the major reaction pathways, for example, cyclization ( syn ) and fragmentation ( anti ), adopted by the diastereomeric 1,4‐radicals of ketones 2 have permitted unprecedented diastereomeric discrimination in their lifetimes to be observed by nanosecond laser flash photolysis. From quantum yield measurements and transient lifetime data, the absolute rate constants for cyclization and fragmentation of a pair of diastereomeric triplet 1,4‐biradicals have been determined for the first time.