Addition of in situ reduced amidinato-methylaluminium chloride to acetylenes

Abstract

Two ethylene-bridged methylaluminium amidinates and one aluminium amidinate containing three terminal trimethylstannyl-ethynyl groups interconnected by π-coordinated potassium ions were prepared in situ. The re-oxidation of the ethylene-bridged compound by iodine followed by further reduction using the same activation procedure demonstrated the versatility of the approach. The reactivity of an ethylene-bridged methylaluminum amidinate towards HCl was examined to demonstrate the building block concept. DFT calculations were performed to gain insight into the mechanism of the in situ activation of diphenylacetylene.

Reductive anti-dimagnesiation and dialumination of alkynes: Synthesis and reactions of trans-1,2-dimetalloalkenes

“…2) Å) with those in the reported 1,2dimagnesioethene 14 and 1,2-dialuminoethenes. [15][16][17] Having the isolated 1,2-dimetalloethenes 2a iPr (thf)4 and 5a Et (thf)2 in hand, we resorted to demonstrating reactivity similar to that described in Figure 2c and 3b. 1,2-Dimagnesioethene 2a iPr (thf)4 underwent the copper-catalyzed hydroxyalkylation using isobutylene oxide to afford 4ab in 80% yield (Figure S2a).…”

“…Contrary to its promising utility, there are quite a few methods for generating reactive 1,2-dimetalloalkenes. [13][14][15][16][17][18] The limited research would originate from the following reactivity-stability trade-off issues: 1) Electron injection into alkynes requires strong reductants such as alkali metals and solvated electrons. 2) After the electron injections from alkali metal occur, the resulting radical anion intermediates and the 1,2-dimetalloalkene products are too unstable to use for organic synthesis.…”

“…Bulky diiminatoaluminum chloride complexes are also known to undergo anti-dialumination in the presence of potassium metal via an addition of an aluminum-centered radical to alkynes. 17,18 However, these complexes are ingeniously designed and decorated with special ligands, thus being not readily accessible. Furthermore, the generated 1,2-dimetalloalkenes were not used for organic synthesis but were examined to undergo simple protonolysis, iodonolysis, and transmetalation to zinc.…”

Synthesis of trans-1,2-dimetalloalkenes through reductive anti-dimagnesiation and dialumination of alkynes

“…The resulting 1,2-dimetalloalkenes should engage in further bond formations at the two reactive carbon-metal bonds to provide a wide variety of multisubstituted alkenes that are otherwise difficult to synthesize. Despite this promising utility, few methods for generating polar reactive 1,2-dimetalloalkenes have been reported [13][14][15][16][17][18] . The limited research is considered to be due to the following reactivitystability trade-off issues.…”

“…1e). Bulky diiminatoaluminium chloride complexes are also known to undergo anti-dialumination in the presence of potassium metal via the addition of an aluminium-centred radical to alkynes 17,18 . However, these complexes are ingeniously designed and decorated with special ligands, and are thus not readily accessible.…”