Chlorides alkynyl

Under similar conditions (diethyl ether or THF as solvent) the reaction of lithium alkynylides with methanesulfonyl chloride (CH35O2CI) gave the corresponding alkynyl sulfones in low to moderate yields. 

The alkynyl ketones 840 can be prepared by the reaction of acyi chlorides with terminal alkynes, Cul in the presence of Et3N is the cocatalyst[719]. (1-Alkynyl)tributylstannanes are also used for the alkynyl ketone synthesis[720]. The a,. 3-alkynic dithio and thiono esters 842 can be prepared by the reaction of the corresponding acid chloride 841 with terminal alkynes[721,722]. 

Terminal alkynes react with propargylic carbonates at room temperature to afford the alka-l, 2-dien-4-yne 14 (allenylalkyne) in good yield with catalysis by Pd(0) and Cul[5], The reaction can be explained by the transmetallation of the (7-allenylpailadium methoxide 4 with copper acetylides to form the allenyKalk-ynyl)palladium 13, which undergoes reductive elimination to form the allenyl alkyne 14. In addition to propargylic carbonates, propargylic chlorides and acetates (in the presence of ZnCb) also react with terminal alkynes to afford allenylalkynes[6], Allenylalkynes are prepared by the reaction of the alkynyl-oxiranes 15 with zinc acetylides[7]. 

Thioketenes can be prepared in several ways, from carboxyHc acid chlorides by thionation with phosphoms pentasulfide [1314-80-3] 2 5 ketene dithioacetals by -elimination, from l,2,3-thiadia2oles with flash pyrolysis, and from alkynyl sulfides (thioacetylenes). The dimeri2ation of thioketenes to 2,4-bis(alkyHdene)-l,3-dithietane compounds occurs quickly. They can be cleaved back pyrolyticaHy (63). For a review see Reference 18. 

This Au(I) complex was tested as co-catalyst in palladium-catalyzed alkynylation reactions but this derivative is much less active than the analogous chloride complex [AuCl(tht)] needing over twice as long to fully convert the starting material [42]. 

An indium chloride-catalyzed coupling of alkynes to aldehydes was also possible in giving a, (J>-unsaturatcd carbonyl compounds in water in low yields (Eq. 8.88).223 (Alkynylation is discussed in Chapter 4 on alkynes.)... 

Improved conditions for the cyclisation of 2-alkynyl diazonium salts to cinnolines, using aqueous sodium chloride, have been described <06OPPI476>... 

An alternative route to allenyl stannanes involves organocuprate displacements on propargylic chlorides bearing an alkynyl PhsSn substituent (equation 39)79. Interestingly, transmetallation by attack of the cuprate on the tin substituent is not observed in these systems. A parallel strategy can be employed for allenylgermanes (equation 39)79. The... 

Nozaki-Hiyama-Kishi (NHK) reactions215,216 are well known and often employed as a useful method for the synthesis of natural products by coupling of allyl, alkenyl, alkynyl, and aryl halides or triflates with aldehydes. The organochromium reagents are prepared from the corresponding halides or triflates and chromium(ll) chloride, and are employed in polar aprotic solvents (THF, DMF, DMSO, etc.). Subsequently, it was found that nickel salts exhibited a significant catalytic effect on the formation of the C-Cr bond217,218 (Equation (19)). 

Yields of the coupling products with alkynyl bromides are relatively low as compared with those obtained with allyl chloride or benzyl chloride. One reason for this is the instability of the product. The dienediynes 51 are slowly cyclized under the influence of light to give pentacyclic dimers 52 (Eq. 2.36), one of which has been characterized by X-ray analysis. 

Access to non-terminal ( ,2)-dienes and ( ,Z, )-trienes 61 is provided analogously through deprotonation of ( , )-4-alkyl-l-chloro-l,3-butadienes followed by insertion of the resultant carbenoid 60 into alkyl- and alkenyl-zirconocene chlorides (Scheme 3.14) [38], The corresponding internal (Z,Z)-dienes and (Z,Z, )-trienes are also readily obtained by insertion of (3-alkynyl carbenoids 62 [44] into alkyl- and alkenylzirconocene chlorides, respectively (Scheme 3.14). Reduction of the triple-bond moiety in the products 63 to afford the cis-alkenes is well known [45—47]. 

The Sonogashira reaction is of considerable value in heterocyclic synthesis. It has been conducted on the pyrazine ring of quinoxaline and the resulting alkynyl- and dialkynyl-quinoxalines were subsequently utilized to synthesize condensed quinoxalines [52-55], Ames et al. prepared unsymmetrical diynes from 2,3-dichloroquinoxalines. Thus, condensation of 2-chloroquinoxaline (93) with an excess of phenylacetylene furnished 2-phenylethynylquinoxaline (94). Displacement of the chloride with the amine also occurred when the condensation was carried out in the presence of diethylamine. Treatment of 94 with a large excess of aqueous dimethylamine led to ketone 95 that exists predominantly in the intramolecularly hydrogen-bonded enol form 96. 

The inverse isomerization mode, providing allenyl thioethers from alkynyl thioethers, is also known [309, 310] for example, 124 is first deprotonated with n-butyllithium and then protonated with ammonium chloride [311] (Scheme 1.55). 

Treatment of allene (1,2-propadiene) with 2equiv. of butyllithium leads to an intermediate dilithio species which adds to ketones and aldehydes to afford homopropargylic alcohols in high yield (Table 9.3) [7]. This intermediate also reacts with geranyl chloride to afford the alkynyl coupling product uncontaminated by the allene regioisomer. 

The cross-coupling reactions of allenes with components containing sp-carbon atoms are useful synthetic transformations since they provide yne-allenes and enyne-allenes, respectively. Due to the synthetic potential of these classes of carbon-rich unsaturated compounds, the scope and limitations were systematically investigated [1, 16-18]. The first synthetic application was reported in 1981, describing the preparation of alkynyl-substituted allenes by coupling of alkynylzinc chlorides with allenyl halides (Scheme 14.8) [11]. 

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