Premium
Photochemistry of α‐Diketones in Carbohydrates: Anomalous Norrish Type II Photoelimination and Norrish–Yang Photocyclization Promoted by the Internal Carbonyl Group
Author(s) -
AlvarezDorta Dimitri,
León Elisa I.,
Kennedy Alan R.,
Martín Angeles,
PérezMartín Inés,
RiescoFagundo Concepción,
Suárez Ernesto
Publication year - 2014
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.201303843
Subject(s) - chemistry , regioselectivity , photochemistry , excited state , ketone , hydrogen atom , diketone , carbonyl group , stereochemistry , group (periodic table) , catalysis , organic chemistry , physics , nuclear physics
A series of four α‐diketones placed as 1α‐pyruvoyl tethers on D ‐glucopyranose and D ‐glucopyranosiduronic acid skeletons was prepared in order to determine the influence of captodative and stereoelectronic effects on the regioselectivity of the hydrogen atom transfer (HAT) in Norrish type II photochemical processes. We observed that the 1,5‐HAT regioselectivity can be switched between the two potentially abstractable syn ‐1,3‐diaxial hydrogens at H6 and H8. Highly unusual photoproducts from Norrish type II photoelimination and Norrish–Yang photocyclization initiated by the excited internal carbonyl group were obtained, in some cases in excellent synthetic yield. The 1,5‐HAT transition state in the Norrish type II photoelimination was investigated by photochemical experiments in the crystalline state.