Reactivity of Quinones with Phosphagermaallene Tip(<i>t</i>Bu)Ge=C=PMes* Leading to Four‐ and Six‐Membered Heterocycles with an Exocyclic P=C Double Bond

Abstract

Abstract Phosphagermaallene Tip( t Bu)Ge=C=PMes* ( 1 ) (Tip = 2,4,6‐triisopropylphenyl, Mes* = 2,4,6‐tri‐ tert ‐butylphenyl) reacts with one equivalent of p ‐quinone (1,4‐benzoquinone, 2,3,5,6‐tetramethyl‐1,4‐benzoquinone, 1,4‐naphthoquinone, and 9,10‐anthraquinone) to form spiro 1‐oxa‐2‐germacyclobutane compounds 2 – 5 with an exocyclic P=C double bond by [2 + 2] cycloaddition between the Ge=C and one of the C=O double bonds. With two equivalents of 1 a double [2 + 2] cycloaddition occurs involving both unsaturated C=O bonds of 1,4‐benzoquinone to give the dispiro compound 6 . [2 + 4] Cycloadditions are observed between the Ge=C double bond of 1 and the O=C–C=O unit of an α‐diketone (benzil) and an o ‐quinone (9,10‐phenanthrenequinone) to give the corresponding 1,4‐dioxa‐2‐germa‐5‐cyclohexenes 7 and 8 .