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[4 + 2] Cycloaddition of Vinylphosphine Oxides to α‑Oxy‑o‑xylylene as a route to Phosphorylated Naphthyl and Biaryl Scaffolds

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journal contribution
posted on 11.01.2019, 00:00 by Sławomir Frynas, Elżbieta Łastawiecka, Anna E. Kozioł, Anna Flis, K. Michał Pietrusiewicz
α-Oxy-o-xylylene, a highly reactive diene readily accessible from benzocyclobutenol, undergoes Diels–Alder reaction with vinylphosphine oxides, yielding the corresponding 2-phosphorylated 1-hydroxy-1,2,3,4-tetrahydronaphthalenes in excellent yields. Use of unsubstituted and trans-2-aryl-substituted vinylphosphine oxides leads to cycloadducts with complete regioselectivity and with cis/trans selectivity up to 19:1 in the most favorable case. In the case of P-stereogenic trans-2-aryl-substituted vinylphosphine oxides, a virtually complete chirality transfer from P to C can be achieved. Dehydration and aromatization of the obtained cycloadducts bearing the resolved P-stereogenic phosphinoyl groups can be carried out to afford the valuable P-stereogenic and axially chiral phosphorylated 1,2′-binaphthyl ring system. Cases of restricted rotation around Csp3–Csp2 single bond in some tetrahydronaphthalene cycloadducts have also been revealed.