Reactivity of Quinones with Phosphagermaallene Tip(tBu)Ge=C=PMes* Leading to Four‐ and Six‐Membered Heterocycles with an Exocyclic P=C Double Bond

Abstract

Phosphagermaallene Tip(tBu)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.

Versatile 1,2- and 1,3-Dipole Behavior of the 1-Arsa-3-Germaallene Tip(t-Bu)Ge═C═AsMes*: Formation of a Heterocyclic Arsa(germa)carbene (AsGeHC)

“…No reaction was observed in the case of selenium with the lone pair on arsenic. Similar results have been obtained between the related phosphagermaallene Tip( t -Bu)GeCPMes* and fluorenone, 9,10-phenanthrenequinone, and nitrone, whereas with selenium (exclusive formation of the corresponding three-membered heterocycle) and benzil (sole formation of a [2 + 4] cycloadduct) slightly different reactions were reported.…”

“…Note that [2 + 4] cycloadditions are generally observed between benzil and doubly bonded main group elements: for example, the silene (Me 3 Si) 2 SiC(OSiMe 3 )R (R = t-Bu, Ad) 23 or phosphagermene Mes 2 GePMes*. 24 The great variety of reactions of the GeC double bond with benzil must be emphasized, since with the closely related phosphagermaallene 8, the sole [2 + 4] cycloaddition was observed, 25 whereas with germene Mes 2 GeCR 2 9 an unexpected epoxidation reaction occurred 26 (Scheme 5); in contrast, the GeC double bond of the transient germavinylidene [Me 3 SiNP(Ph 2 )] 2 CGe does not react with benzil, only a [1 + 4] cycloaddition with the germylene function occurring. 27 X-ray determinations from single crystals obtained by slow crystallization from pentane unambiguously confirmed the structures of 2 (Figure 1), 3 (Figure 2), 4 (Figure 3), 5 (Figure 4), and 7 (Figure 5).…”

Potassium 2-germanaphthalenide: an isolable polycyclic system of germanium-incorporated anionic benzenoid

“…K + · 5 − is expected to behave both as a divalent-germanium species (germylene) and a GeC double bond species (germene or germenide). The reactivity of both species with diphenylethanedione (benzil), an α-diketone compound, has been disclosed so far, giving a [1 + 4]-cycloadduct from germylene 39 and a [2 + 4]-cycloadduct from germene, 40 respectively. The reaction of K + · 5 − with two equivalents of benzil completed in 5 min to afford compound K + (thf)· 7 − as a sole product as confirmed by 1D- and 2D-NMR spectroscopy (Scheme 3).…”

Versatile Stereoselective Cycloadditions between Heterocumulenes and Phosphagermaallene Tip(tBu)GeCPMes*: Experimental and Theoretical Investigations

“…Intracyclic GeÀC bond lengths (8 1.983(8) and 10 1.980 (3) ) are in the normal range but at the upper limit of the range (standard GeÀC bond lengths 1.94-1.98 [15a] ), with three of the four acyclic GeÀC bonds being slightly longer up to 2.009 (10) . The GeÀS bond lengths (8 2.295(3) and 10 2.258(1) ) are also in the normal range (2.21-2.29 [15a] ).…”

“…C double bond: [2+1] with sulfur, selenium, or tellurium; [8] [2+2] with aldehydes and ketones, [7] a-ethylenic aldehydes, [9] p-quinones, [10] and pivalonitrile; [11] and [2+4] with a-ethylenic ketones [9] (Scheme 1). CÀH insertion with acetonitrile [11] and ene-reactions with compounds that present a slightly acidic hydrogen (acetophenone, [7] methyl vinyl ketone [9] ) have also been observed.…”