Lithium phenylacetylide

Four equivalents of lithium phenylacetylide reacted with bis bis(trimethylsilyl)amido zinc (Scheme 51) to form the ion-paired dilithiotetra(phenylacetylido)zincate 65, whose structure is shown in Figure 33.121 The zinc-carbon bonds (2.05 A) are somewhat longer than those observed in the tri(phenylacetylido)zincate 62a, due to the increase in both the coordination number and the negative charge on the ion. Each lithium ion is associated with the zincate ion through coordination to two of the triple bonds. 

Phenyl(p-methoxyphenyltelluro)acetylene (typical procedure To a solution of lithium phenylacetylide (20.0 mmol), prepared as described above, is added dropwise a solution of p-methoxyphenyltellurenyl bromide (prepared by adding bromine (1.60 g, 10.0 mmol)) in benzene (5 mL) to a solution of the corresponding ditelluride (4.69 g, 10 mmol) in THF (10 mL) at 0°C under Nj. The reaction mixture is stirred for 1 h at room temperature and then treated as described above to give the product (4.90 g (73%)), which is recrystallized from EtOH (m.p. 71-72°C). 

Lithium phenylacetylide was trifluoromethylated with the less powerful Se-triflate 26 in high yield (Eq. 20). 

Wen and Grutzner used, among other NMR parameters, the QSC of the lithium enolate of acetaldehyde to deduce that it exists as tetramers of different solvation in THF and THF/n-hexane solvent systems . However, the most thorough study of Li QSC and the most interesting in the present context was reported by Jackman and coworkers in 1987167 -pjjg effects on the QSC values of both aggregation and solvation in a number of organolithium systems was studied in this paper, i.e. different arylamides, phenolates, enolates, substituted phenyllithium complexes and lithium phenylacetylide. 

With 2-unsubstituted quinazolines 426 (X = O or S), organometallic addition occurs at the 2-position to give 2-alkyl-l,2-dihydroquinazolines 428 <2005JSF121, 2005S2951>, while with 2-alkoxyquinazolines addition of orga-nometallics occurs at the 4-position, as demonstrated by the addition of lithium phenylacetylide to the 2-methoxy-methyl quinazolinone 429 which gave a quantitative yield of a tautomeric mixture of the 3,4- and 1,4-dihydro derivatives 430 and 431 <2004JA5427>. 

Preparation of l-Chloro-2-phenylacetylene from Lithium Phenylacetylide and Chlorine... 

Cyclopentanones. Enamines (2) react with 1 at 25° to give in high yield the keto nitriles 3, which undergo the expected addition of lithium phenylacetylide to provide 4. On treatment of 4 with (C6H5)3SnH (AIBN) a 5-acetylenic radical is formed, which cyclizes to a benzylidenecyclopentane (5). Ozonolysis of 5 provides cyclopentanone 6. 

Alkynylvanadium(III) chloride, 219 Butyllithium, 56 Chromium(II) chloride, 84 Lithium phenylacetylide, 244 Organocerium reagents, 206 Titanium(IV) chloride, 304 By other methods (2R,4R)-Pentanediol, 237... 

Lithium butyldimethylzincate, 221 Lithium sec-butyldimethylzincate, 221 Lithium-Ethylamine, 158 Lithium o-lithiophenoxide, 166 Lithium methoxyacetylide, 166 Lithium phenylacetylide, 244 Lithium trialkylzincates, 221 Lithium trimethylsilylacetylide, 206 Lithium trimethyl(tributylstannyl)-aluminate, 320... 

Di(phenylethynyl)-2,3-dihydrobenzo[6]thiophene-2,3-diol (165) is obtained on treating benzo[6]thiophene-2,3-quinone with lithium phenylacetylide. It is converted into 2,3-di(phenylethynyl)benzo[6]-thiophene on treatment with stannous chloride.472... 

The following is a typical example of a process described by Russian workers as "anionic activation", and used for the rapid construction of fluoro-substituted heterocycles Treatment of 2-(trifluoromethyl)aniline with either lithium phenylacetylide or the lithium enolate of acetophenone in THF at -60°C gave 4-fluoro-2-phenylquinoline in 25-40% yield. 

Reactivity of copper dicationic 104 with alkynes is of interest (98JCS(D) 1115). Thus, with lithium phenylacetylide, the acetylide counterpart constitutes a g,r 1-bridge between two copper sites as in 105, while MeOOCC=CCOOMe performs the (i,x 2-bridging function 106 as a whole. 

The mechanism of acylation of lithium phenylacetylide with a Weinreb amide has been investigated (Scheme 10).71 Dimeric lithium acetylide has reacted via a mono-solvated monomer-based transition structure. The robust tetrahedral intermediate (12) forms sequentially a C(l) 2 2 mixed tetramer with the excess lithium acetylide and a 1 3 (alkoxide-rich) mixed tetramer. The stabilities of the mixed tetramers are consistent with a pronounced autoinhibition. 

The first alkynyliodonium salt, (phenylethynyl)phenyliodonium chloride, synthesized in low yields from (dichloroiodo)benzene (3) and lithium phenylacetylide (equation 1), was reported in 196526. This chloride salt is unstable and readily decomposes to a 1 1 mixture of chloro(phenyl)acetylene and iodobenzene. It was not until the 1980s, however, that alkynyliodonium salts became generally available. This was made possible by the introduction of sulfonyloxy-/l3-iodanes as synthetic reagents46 and by the recognition that iodosylbenzene (4) can be activated either with boron trifluoride etherate or with triethy-loxonium tetrafluoroborate31. These reagents are now widely employed for the conversion of terminal alkynes and their 1-silyl and 1-stannyl derivatives to alkynyliodonium salts (equations 2 and 3). A more exhaustive survey of iodine(III) reagents that have been... 

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

Alkynylation of aziridines can be effected through the copper-catalyzed ring opening with acetylides. For example, lithium phenylacetylide engages in smooth nucleophilic attack of A-tosyl-7-azabicyclo[4.1.0]heptane 160 in the presence of copper(i) triflate to provide the cyclohexyl alkyne 161 in excellent yield (Scheme 42) <2004SL1691>. 

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. 

Aryl tellurium halides condense with lithium phenylacetylide and aromatic lithium compounds. ... 

Treatment of the aldehyde 148 with lithium phenylacetylide yielded another versatile intermediate (149), which could be transformed, after stereoselective partial reduction to the corresponding tram allylic alcohol (150), either by simple deprotection to racemic 36 or first by oxidation and then deprotection to the diketone 39. Elimination of water from the ketol 36 gave 8, which could be reduced with diisobutyl aluminum hydride without affecting the double bond to the dienol 48. ... 

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... 

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