Photooxygenation of chiral allylic alcohols: hydroxy-directed regio- and diastereoselective ene reaction of singlet oxygen

Diastereoselective schenck ene reaction of singlet oxygen with chiral allylic alcohols; access to enantiomerically enriched 1,2,4-trioxanes

“…[18][19][20][21][22] The diastereoselectivity of singlet oxygen photooxygenation of chiral allylic alcohols in non-polar solvents yields threo-b-hydroperoxy alcohols as the major product. [19][20][21][22][23][24][25][26][27] The hydroxy-directed regio and diastereoselective photooxygenation of chiral alcohols, to yield allylic hydroperoxides, was first discovered by Adam et al 26 Griesbeck et al utilised this diastereoselective photooxygenation to synthesise racemic threo-b-hydroperoxy alcohols that were in turn used to synthesise diastereomerically pure racemic chiral 1,2,4-trioxanes similar to trioxanes 1-8. [12][13][14]20,28 Dye-sensitised photooxygenation of achiral allylic alcohols has been used by Chandan Singh to obtain b-hydroperoxy alcohols, which were then used to synthesise 1,2,4-trioxanes.…”

A Mechanistic Spectrum of Chemical Reactions

“…Hydrogen bonding to the pendant (tailing) oxygen (Scheme 21) in the perepoxide quasi-intermediates controls the facial/diastereoselectivty of the ene reactions of 42 S. Inagaki singlet oxygen with allylic alcohols [106,107] and amines [108,109]. The allylic alcohol exhibits a striking diastereoselectivity for the threo (S*S*) b-hydroxy allylic hydroperoxide while its acylated derivative exhibits a modest erythro (S*R*) diastereoselectivity.…”

Selective Formation of Allylic HydroperoxidesviaSinglet OxygeneneReaction

“…The high diastereoselectivity observed in the photooxygenation of certain chiral allylic alcohols 45,46 , amines 47,48 and derivatives, which will be analysed in Section III.B.1, was rationalized in terms of hydroxyl or amino group coordination with the incoming oxygen. The synergy of oxygen-hydroxyl coordination as well as the 1,3-allylic strain provides, in non-polar solvents, high selectivity for the threo allylic hydroperoxides.…”

“…Singlet oxygen affords a variety of regio and diastereoselective reactions with chiral allylic alcohols 45,46,140 , amines 47,48,193 (e.g. substrate 161, Scheme 58) and chiral cyclohexadienes 91, 92 that are useful for synthetic transformations.…”