ISSN:
0170-2041
Keywords:
Singlet oxygen
;
Oxygen transfer
;
Terpenes
;
Ene reaction
;
Selectivity, regio-, stereo-
;
Epoxidation
;
Alcohols, allylic epoxy
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The photooxygenation of α-ionone (4) in different solvents leads, with higher than 90% regioselectivity, to a mixture of two diastereomeric allylic hydroperoxides 5a and 5b (diastereomeric ratio 77:23). These compounds are transformed in the presence of Ti(OiPr)4 into the corresponding epoxy alcohols 8a and 8b (cis selectivity) and the allylic alcohols 7a and 7b with high diastereoselectivity. In these cases the substrate configuration exhibits a pronounced control of type selectivity: the cis allylic hydroperoxide 5a is preferentially reduced to the allylic alcohol 7a, whereas the diastereomeric trans compound 5b is preferentially (syn selectivity) converted to the epoxy alcohol 8b. Epoxidation of the allylic alcohol 7a with meta-chloroperbenzoic acid leads, in contrast to the Ti(IV)-catalyzed reaction, to a mixture of diastereomeric epoxy alcohols 8a and 8c, with the anti product 8c as major diastereomer (diastereomeric ratio 28:72). These reactions serve as a route to three of the four possible diastereomeric epoxides of 3-hydroxy-γ-ionone.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.199219920136
Permalink