Lithium phenylacetylide, reaction with

The direct introduction of an acetylide moiety, using pyridine A-oxide (or quinoline, diazine and triazine iV-oxides) can be achieved in a comparable way, by reaction with potassium phenylacetylide reaction with the lithium salt requires addition of acetyl chloride at the end of the reaction to aromatise. At low temperature, and using i-PrMgCl, 2-metallation of pyridine iV-oxides can be achieved, and thus, the introduction of electrophiles at the 2-position. ... 

An unexpected reaction occurs when p-fluorotoluenetricarbonylchromium complex 18e is treated with lithium phenylacetylide (generated from nBuLi and phenylacetylene) in THF... 

From alcohols. Alcohols can be transformed into phenylselenides in a stepwise manner via mesylation and reaction with lithium phenylselenolate. This procedure offers obvious advantages over the formation of the corresponding bromides or iodides when subsequent reaction with strong nucleophiles, such as organolithium compounds, are necessary to prepare the radical precursors. The diol 8 is converted to the bis(phenylselenide) 9 via the corresponding bis(mesylate) as shown in Scheme 2 [6]. Compound 9 is converted to the radical precursor 11 via reaction with lithium phenylacetylide followed by alkylation with allylbromide and a Pauson-Khand reaction. Such a reaction sequence would not be feasible with an alkyl halide. The cyclization afforded the expected tricyclic compound 12 in 95% yield. 

One of the characteristic features of this approach is the successful fert-alkyl-al-kynyl coupling with dialkylaluminum alkynides which enables the introduction of a quaternary carbon in a position adjacent to an alkynyl group. Such transformation was previously achieved by the cross-coupling of ferf-alkyl chlorides with trialkynyl-aluminums as already described in this section [92]. The reaction of 98 with dimethyl-aluminum phenylacetylide (1.5 equiv.), readily prepared from lithium phenylacetylide and Me2AlCl, in toluene at -78 °C for 30 min resulted in formation of a cross-coupling product in 70 % yield. This result indicates the efficient and selective transfer of the alkynyl group from the aluminum center in dialkylaluminum alkynides as depicted in Sch. 65. 

Course of Reactions. - 3.3.1 Groups 1 and 2. 6Li, 13C and 19F NMR spectra were used to follow reactions of lithium phenylacetylide, PhC=CLi, with quinazolines.1114 111 NMR monitoring of reactions of R2Mg with KOR shows the formation of the species [R2Mg( i-OR )2MgR2]2, where R = hexyl, neopentyl, sec-butyl etc., R = Me, Et, Bu, Ph etc..1115... 

Reactions. - The reactions of diorganoiodophosphines with varying quantities of iodine have been studied by NMR techniques, which indicate the formation of a dialkyldi-iodophosphonium iodide as the initial product, followed by polyhalide anion formation in the presence of excess iodine. A modified McCormack synthesis of 3-silylated phosphol-3-enes (168) from phenyl-dichlorophosphine and 2-silylated 1,3-butadienes has been described. The reaction is carried out in the presence of a small amount of copper stearate in acetic anhydride at 50 °C, these conditions preventing the complete desilylation observed under standard conditions. The consecutive reaction of lithium phenylacetylide with triphenylborane and diphenylchlorophosphine results in the formation of the intramolecularly coordinated phosphino-borane (169). Treatment of the alkoxyvinyldichlorophosphines (170) with Grignard reagents... 

S)-BINOL-Ti was also shown to be an effective chiral catalyst for the catalytic asymmetric addition of alkynylzinc to inactivated simple ketones with good to excellent enantioselectivities [63] (Scheme 14.12). The same reaction has been furnished by using lithium phenylacetylide as the nucleophile under the catalysis of titanium complex prepared from BINOL and ClTi(O Pr)3 [64]. 

Alkoxy-substituted Tj -cyclohexadienyliumiron complexes are less frequently applied to nucleophilic substitution. Reaction of the T -l-ethoxycyclohexadienyliumiron complex salt with lithium phenylacetylide leads to ipso substitution. Treatment of the resulting (r] -cyclohexadiene)iron complex with acid affords the 1-phenylethynyl-substi-tuted Tj -cyclohexadienyliumiron complex salt by elimination of ethanol (Scheme 4-174). 

Carbodiitnides (332 Scheme 55) form amidines on treatment with NaBH4 in alcohols, Grignard reagents, sodium phenylacetylide, carbon monoxide in the presence of s-butyl- or t-butyl-lithium and nitrones catalyzed by HBF4. In the reaction of stannylated or silylated ynamines with carbodiimides... 

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