Synthesis of tri-and tetraalkynylgermanes

Abstract

A straightforward synthesis of tetra and trialkynylgermanes by reactions of compounds containing Ge-N or Ge-Cl bonds with alk 1 ynes was proposed. Reactions of appropriate amino or halogermanes with alk 1 ynes were effective only in the presence of an equivalent amount of zinc dihalide.Acetylene derivatives of germanium, in which the Ge atom is bound to sp hybridized C atoms, are well known and are conventionally synthesized by reactions of alkali metal or magnesium alkynides with halogermanes. 1,2However, direct replacement of the acid H atom in alk 1 ynes by germanium has been reported for only a few cases, 3,4 in contrast to similar reactions of alk 1 ynes with compounds containing Sn-Cl, 5 Sn-O, 6 Sn-N, 7 and Pb-O bonds. 8 Earlier, 9 we have shown that dialkylamino silanes react with alk 1 ynes in the presence of zinc dihalides to give silylalkynes in high yields.Here we found that reactions of tetrakis(dialkyl amino)germanes 1 and tris(dialkylamino)phenylgermanes 2 with alk 1 ynes 3 in dioxane or THF at 70-100 °C in the presence of zinc dihalides afford alkynylgermanes in high yields (Scheme 1; Tables 1, 2). Scheme 1 n = 0; NR 2 2 = NEt 2 (1a), N(CH 2 ) 5 (1b); R 3 = Bu (3a, 4a), Me 3 Si (3b, 4b), Ph (3c, 4c), CH 2 OAc (3d, 4d), C 6 H 13 (3e, 4e), 4 BrC 6 H 4 (3f, 4f); 1 C 10 H 7 (3g, 4g); n = 1; R 1 = Ph; NR 2 2 = NEt 2 (2a), N(CH 2 ) 5 (2b); R 3 = Bu (3a, 5a), Me 3 Si (3b, 5b), Ph (3c, 5c); Hal = Cl, BrWith an excess of the acetylene component, three or four amino groups were exhaustively replaced in the reac tions with tris(dialkylamino)phenylgermanes 2 or tetra kis(dialkylamino)germanes 1, respectively. In the absence of zinc dihalides, the reaction did not occur even at el evated temperatures. This distinguishes tri and tetra aminogermanes from trialkyl(amino)germanes, which react with alk 1 ynes at 150-180 °C for a long time. 3,4The starting tris and tetrakis(dialkylamino)germanes are easily accessible via reactions of secondary amines with appropriate halogermanes. 14 When used in excess, these amines serve as a reaction medium and provide virtually quantitative yields of aminogermanes 1 and 2.We also found that germanium tetrachloride and trichloro(phenyl)germane in the presence of zinc dihalides react with alk 1 ynes differently from what has been re ported earlier. 15 The presence of zinc dihalide increases the alkynylation degree and allows one to obtain tetra alkynylgermanes from germanium tetrachloride and trialkynyl(phenyl)germane from trichloro(phenyl)ger mane (Scheme 2). Scheme 2 n = 0; R 2 = Me 3 Si (3b, 4b), Ph (3c, 4c), CH 2 OAc (3d, 4d); n = 1; R 1 = Ph; R 2 = Bu (3a, 5a), Me 3 Si (3b, 5b), Ph (3c, 5c)The yields of tetraalkynylgermanes 4 and trial kynyl(phenyl)germanes 5 were up to 85 and 75%, respec tively. We found this method to be inapplicable to trialkylchlorogermanes and dialkyl(dichloro)germanes: they did not react with alk 1 ynes in the presence of

Cooperative Ge–N Bond Activation in Hydrogallation Products of Alkynyl(diethylamino)germanes (Et2N)nGe(C≡CtBu)4–n

“…No reaction was observed when the tris­(alkynide) 1 was stirred with PhCCH at room temperature or heated for more than 30 h at 80 °C. It has been reported that the related reaction of (R 2 N) n GeR′ 4– n with alkyl- or arylacetylenes R″CCH to yield R′ 4– n Ge­(CCR″) n ( n = 0, 1) required stoichiometric amounts of Lewis acidic zinc dihalides for activation . The unique reaction and the unexpectedly high reactivity of 4b is a clear indication of the cooperative activation of the Ge–N bond by the Lewis acidic Ga t Bu 2 group.…”

“…It has been reported that the related reaction of (R 2 N) n GeR′ 4−n with alkyl-or arylacetylenes R″CCH to yield R′ 4−n Ge(CCR″) n (n = 0, 1) required stoichiometric amounts of Lewis acidic zinc dihalides for activation. 18 The unique reaction and the unexpectedly high reactivity of 4b is a clear indication of the cooperative activation of the Ge−N bond by the Lewis acidic Ga t Bu 2 group. Despite the prolonged heating of the reactants at 60 °C during the synthesis of compound 5, no indication for a cis/trans isomerization of the vinyl groups was found.…”

New Catalytic Route to Alkynylgermanes

“…Alkynylgermanium compounds can be prepared by various methodologies involving classical stoichiometric organometallic routes that can be classified into three groups, i.e., the reactions of organogermanium halides with metal acetylides, germylation of terminal alkynes, and modification of preformed alkynylgermanes 8 (for a recent review see ref ).…”

Synthesis of Alkynylsilanes: A Review of the State of the Art

“…Later, Andreev expanded upon this concept by devising a zinc halide-assisted sp CÀ H germylation involving the reaction between alkynes and aminogermanes. [171] Very recently, Bannykh and Pihko disclosed a metal-free sp CÀ H silylation protocol. Here, a quaternary ammonium pivalate serves as the catalyst, whilst N,O-bis(silyl)acetamides as silylating agents (Figure 44).…”

“…Finally, the authors proposed two independent mechanistic pathways. Later, Andreev expanded upon this concept by devising a zinc halide‐assisted sp C−H germylation involving the reaction between alkynes and aminogermanes [171] …”