Regio- and stereoselectivity of the Norrish-Yang photocyclization of dialkyl 1,2- diketones. Solution versus solid state photochemistry of two polymorphs

Alvarez-Dorta, Dimitri and León, Elisa I. and Martín, Ángeles and Kennedy, Alan R. and Pérez-Martín, Inés and Shankland, Kenneth and Suárez, Ernesto (2022) Regio- and stereoselectivity of the Norrish-Yang photocyclization of dialkyl 1,2- diketones. Solution versus solid state photochemistry of two polymorphs. Journal of Organic Chemistry, 87 (21). pp. 14940-14947. ISSN 0022-3263 (https://doi.org/10.1021/acs.joc.2c01855)

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Abstract

As shown by X-ray crystallography, crystals of 3β-acetoxy-16,17-seco-17,20-dioxopregn-5-ene-16-nitrile are dimorphic. The regioselectivity of the Norrish-Yang type II photocyclization under visible light of this steroidal 1,2-diketone, which bears primary, secondary, and tertiary nonequivalent abstractable γ-hydrogens, dramatically increases in the crystalline state of both polymorphs. X-ray crystallography and molecular mechanics calculations reveal crystal structure-solid state photochemistry relationships.