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DOI: 10.1055/sos-SD-037-00246

Griesbeck, A. G.; Sokolova, T.Science of Synthesis, (200837448.

The control of the photocycloaddition regioselectivity with aromatic aldehydes is possible by introducing a directing group into the alkene component: enol ethers and silyl enol ethers (e.g., 81 and 83, respectively) result in exclusive formation of 3-alkoxy- and 3-siloxyoxetanes, e.g. 82 and 84, respectively (Scheme 31).[‌74‌,‌75‌] Additionally, the diastereoselectivity is also controlled in both cases, favoring the syn arrangement between the aldehyde-derived group and the alkoxy or siloxy group.[‌76‌] These reactions proceed via the triplet state of the electronically excited aldehyde, indicating that triplet [2+2] photocycloadditions can be highly regio- and diastereoselective.

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