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).
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.
Moorthy
Jarugu Narasimha
JN
Department of Chemistry, Indian Institute of Technology, Kanpur 208 016, India. moorthy@iitk.ac.in
Koner
Apurba L
AL
Samanta
Subhas
S
Singhal
Nidhi
N
Nau
Werner M
WM
Weiss
Richard G
RG