Transmetallation and silylation products of aminal carbanions

Abstract

Reactions of the lithiated carbanion [(RLi)(2).(RH)] (R = MeN[CH(2)N(Me)](2)CH, 2,4,6-trimethyl-2,4,6-triazacyclohex-1-yl) with dialkylaluminium and -gallium chlorides lead to the corresponding dialkylaluminium and -gallium compounds (RAlMe(2))(2), (RAlEt(2))(2) and (RGaEt(2))(2). They were characterised by elemental analyses, NMR spectroscopy ((1)H, (13)C, (27)Al) and crystal structure determinations. In the solid state the aluminium and gallium compounds form dimers by intermolecular coordination between the metal acceptor and the nitrogen donor leading to six-membered M(2)C(2)N(2) rings in chair conformation. As a first test for the synthetic utility of [(RLi)(2).(RH)], nucleophilic aminomethylation of chlorotrimethylsilane was performed to give RSiMe(3). Further deprotonation of RSiMe(3) with tBuLi occurs at one of the methyl groups bound to the silicon atom leading to RMe(2)SiCH(2)Li. Reactions with dimethylaluminium and -gallium chlorides gave RMe(2)SiCH(2)AlMe(2) and RMe(2)SiCH(2)GaMe(2). The compounds were characterised by NMR spectroscopy ((1)H, (13)C, (29)Si, (27)Al), elemental analyses and single crystal X-ray diffraction. The compounds are monomeric in the solid state with intramolecular M-N bonds (M = Al, Ga) leading to five-membered rings.

Structurally Stimulated Deprotonation/Alumination of the TMP Anion

“…While this reaction is unprecedented, TMP dispensed as Mg(TMP) 2 has been reported 20 to deprotonate LiHMDS (HMDS is 1,1,1,3,3,3-hexamethyldisilazide) at a Si(CH 3 ) site, though this is a much less challenging task as several examples of Si(CH 3 ) deprotonation have appeared. 21 In general, C–H activation of CH 3 groups is a well-known, somewhat random phenomenon across organometallic chemistry. 22 The reaction reported herein represents a special and surprising case of C–H bond activation which introduces a novel modified form of TMP.…”

Carbon‐metalated triazines and tetrazines: Synthesis and reactivity

“…Sterically less hindered dimethyl-and diethylaluminium(III) and gallium(III) monochlorides gave, however, the metalated triazines 192 (Scheme 43). [55] S Reactions of 169 with silyl chlorides afforded the 1,2,3-triazine C-silylation products 193, 194, except for SiCl 4 . In the latter case, an unusual seven-membered 2,4,6-triaza-1,1-dichloro-1-sila-cycloheptane derivative 195 was formed, although in a very low yield (Scheme 44).…”

“…Thus, combining lithiotriazine 169 with di-tert-butyl gallium(III) monochloride furnished the derivative 173 of a formal MeN CH − anion (Scheme 37). [54,55] Even more unexpectedly, when 169 was allowed to react with di-cyclopentadienyl yttrium chloride, the organometallic complex of a new type 172 was isolated (Scheme 37).…”

“…In the latter case, an unusual seven-membered 2,4,6-triaza-1,1-dichloro-1-sila-cycloheptane derivative 195 was formed, although in a very low yield (Scheme 44). [60] Interestingly, lithiation of the silyl-triazines 193 took place selectively at the side-chain methyl group, not at the heterocyclic unit, regardless on the Si atom substitution pattern (Scheme 45), [55,60] and some further exchange reactions with Al and Ga chlorides were reported. [55] Products 196 were mainly isolated by simple precipitation from the reaction mixture.…”

Structurally Stimulated Deprotonation/Alumination of the TMP Anion

“…While this reaction is unprecedented, TMP dispensed as Mg(TMP) 2 has been reported [20] to deprotonate LiHMDS (HMDS is 1,1,1,3,3,3-hexamethyldisilazide) at a Si(CH 3 ) site, though this is a much less challenging task as several examples of Si(CH 3 ) deprotonation have appeared. [21] In general, CÀH activation of CH 3 groups is a well-known, somewhat random phenomenon across organometallic chemistry. [22] The reaction reported herein represents a special and surprising case of C À H bond activation which introduces a novel modified form of TMP.…”