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)

Abstract

The 1-arsa-3-germaallene Tip(t-Bu)GeCAsMes* (1; Tip = 2,4,6-triisopropylphenyl, Mes* = 2,4,6-tri-tert-butylphenyl) reacts with selenium, fluorenone, N-tert-butylphenylnitrone, and 9,10-phenanthrenequinone as a 1,2-dipole by the GeC double bond, to give the corresponding three-, four-, five-, and six-membered-ring derivatives 2–5, respectively. Both [2 + 2] and [2 + 4] cycloadditions involving the GeC double bond are observed between 1 and benzil, leading to the four- and six-membered-ring derivatives 6 and 7. In great contrast, 1 reacts with diphenylketene as a 1,3-dipole by the whole GeCAs unit to afford the transient heterocyclic arsa(germa)carbene 12 according to a [3 + 2] cycloaddition. DFT calculations were carried out to understand this particular behavior. This first heavier analogue of an NHC with an arsenic atom rearranges to the tricyclic compound 11.

Synthesis and Reactivity of Acyclic Germanimines: Silyl Rearrangement and Cycloadditions

“…The addition of carbonyl compounds to germenes is also well established . For instance, the [2 + 2] cycloaddition of germaniumcarbon double bonds across ketones has been reported with germallenes, [(Tip)­( t Bu)­GeCEMes] (E = P, As; Tip = 2,4,6-triisoprophylphenyl). , The germanimine [(Mes) 2 GeNAAN] (AAN = N -dimethylanthranilamide) is postulated to undergo [2 + 2] cycloaddition with 3,5-di- tert -butylorthoquinone; as the expected product is unstable, the only evidence for this pathway was through analysis of the decomposition products …”

“…66 For instance, the [2 + 2] cycloaddition of germaniumcarbon double bonds across ketones has been reported with germallenes, [(Tip)(tBu)Ge CEMes] (E = P, As; Tip = 2,4,6-triisoprophylphenyl). 67,68 The germanimine [(Mes) 2 GeNAAN] (AAN = N-dimethylanthranilamide) is postulated to undergo [2 + 2] cycloaddition with 3,5-di-tert-butylorthoquinone; as the expected product is unstable, the only evidence for this pathway was through analysis of the decomposition products. 69 The reactivity observed between germanimine 3 and phenylacetylene is in contrast to the facile Diels−Alder reactivity of [(NON t B u )GeNMes] (and Baines' [(Mes) 2 GeCR 2 ] compound); 26−29 with germanimine 3, there is no evidence of any type of [4 + 2] pathway occurring, either in the isolated products or reaction mixture.…”

Versatile Reactivity of Phosphagermaallene Tip(t-Bu)Ge═C═PMes* with α-Ethylenic Esters

“…The formation of 8 can be explained only by the intermediate formation of the cyclic germa(phosphino)carbene 9 followed by an insertion of the carbenic carbon atom into a C–H bond of a tert -butyl group in ortho position on the supermesityl group. This type of insertion of a carbene into a C–H bond is well known. , Thus, the phosphagermaallene behaves as a 1,3-dipole in such a reaction, giving a [3+2] cycloaddition with the CHCH 2 moiety. It is worth noting that the more positive part of the CHCH 2 unit (CH 2 ) is bonded to the more positive part of the GeCP (Ge) unit.…”

Synthesis and reactivity of N-heterocyclic carbene (NHC)-supported heavier nitrile ylides

“…Notably, among E 14 –P multiple bonded compounds, the homo or hetero-allenic heavier analogues of nitrile ylides (R 2 E 14 E 15 E 14 R, E 14 = Si–Pb, E 15 = P, Scheme 1c) remains elusive, despite the known constitutional isomers of “heavy heteroallenes” (R 2 E 14 E 14 =E 15 R) that behave as 1,3-dipoles. 34–37 The persistent elusiveness of these compounds underscores the intricate challenges associated with their synthesis, highlighting uncharted territories within the expansive field of heavy main group chemistry. 38,39…”