ISSN:
0170-2041
Keywords:
Photooxygenation
;
Singlet oxygen
;
Ene reaction
;
Hydroperoxy esters
;
Perepoxide, cis effect
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Photooxygenation of methyl (E)- and (Z)-2-methyl-4-phenyl-2-pentenecarboxylates (E-1, Z-1) afforded the hydroperoxy esters (R*,S*)-2a and (S*,S*)-2b through regiospecific and diastereo-selective ene reaction of singlet oxygen at the α-methyl group with a diastereomeric ratio (d.r.) of 2a:2b ca. 80:20 for E-1 and ca. 65:35 for Z-1. The relative configurations of 2a, b were established by chemical correlation through triphenylphosphine reduction of the allylic hydroperoxy esters 2a, b to the allylic hydroxy esters 4a, b and subsequent catalytic hydrogenation to the literature-known saturated hydroxy esters 5a, b (from pure 4a) and 5c, d (from pure 4b). The appreciable diastereoselectivity (d.r. ca. 80:20) observed for the E-1 isomer is explained in terms of the cis effect, by coordinating the allylic hydrogen of the stereogenic C-4 position to the terminal oxygen of the postulated perepoxide-like structure.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.1990199001190
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