Propargyl chloride, reaction

A mixture of 0.40 mol of propargyl chloride and 150ml of dry diethyl ether was cooled at -90°C (liquid nitrogen bath) and a solution of 0.40 mol of ethyl-lithium (note 1) in about 350 ml of diethyl ether (see Exp. 1) was added with vigorous stirring and occasional cooling (note 2). The temperature of the reaction mixture was kept between -70 and -90°C. The formation of the lithium derivative proceeded almost instantaneously, so that the solution obtained could be used directly after the addition of the ethyl 1ithium, which was carried out in 15-20 min. This lithium acetylide solution is very unstable and must be kept below -60°C. 

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]. 

When perfluoroheptylcopper reacted with propargyl bromide, a violent reaction occurred, and less than 10% of the expected allene was obtained [226] However, when propargyl chlorides or tosylates were used as substrates, the expected allenes were obtained m good yields [227] (equation 156)... 

Ruthenium hydride complexes, e.g., the dimer 34, have been used by Hofmann et al. for the preparation of ruthenium carbene complexes [19]. Reaction of 34 with two equivalents of propargyl chloride 35 gives carbene complex 36 with a chelating diphosphane ligand (Eq. 3). Complex 36 is a remarkable example because its phosphine ligands are, in contrast to the other ruthenium carbene complexes described so far, arranged in a fixed cis stereochemistry. Although 36 was found to be less active than conventional metathesis catalysts, it catalyzes the ROMP of norbornene or cyclopentene. 

Rearrangement of acetylenic sulphenates to the allenic sulphoxides 151 was discovered when the synthesis of propargylic ester of trichloromethanesulphenic acid 152 was attempted (equation 86). This reaction is of general scope and gives very good yields of allenic sulphoxides (Table 14) from structurally diverse cohols and various sulphenyl chlorides Reaction of alkynols 153 with benzenesulphenyl chloride in the presence... 

Reduction to Halocarbons. The best conditions for the reductive chlorination of ketones use the reagent combination Me2ClSiH/In(OH)3 (Eq. 241).331 Examples include conversions of aryl ketones to benzyl chlorides, ethynyl ketones to propargyl chlorides, and alkyl ketones to alkyl chlorides (Eq. 242).331 Addition of lithium iodide to the reaction mixture yields the corresponding iodide product. The combination of TMDO/I2 reductively iodinates aryl ketones and aldehydes in good yields (Eq. 243).357... 

Hydride-promoted reactions are also well known, such as the acrylic and vinylacrylic syntheses (examples 7-10, Table VII). Some less-known compounds, which form in the presence of halide ions added to tetracar-bonylnickel, have been described by Foa and Cassar (example 11, Table VII). Reaction of allene to form methacrylates, and of propargyl chloride to give itaconic acid (via butadienoic acid), have been reported (examples 13 and 14, Table VII). 1,5-Hexadiene has been shown to be a very good substrate to obtain cyclic ketones in the presence of hydrogen chloride and tetracarbonylnickel (example 15, Table VII). The latter has also been used to form esters from olefins (example 16, Table VII). In the presence of an organic acid branched esters form regioselectivity (193). 

Similar to the cycloaddition of allyl cations30, allenyl cations have been found to undergo cycloadditions with alkenes to afford bicyclic compounds31. The allenyl cations were generated from propargyl chlorides by treatment with Lewis acids. This reaction sequence proceeds via the cyclization 34 -------> 3532, in spite of the fact that... 

The cycloaddition of allenyl cations with 1,3-dienes results in a number of intermediate cations from which different products result. The allenyl cations 38 are generated first by the reaction of propargyl chlorides with zinc chloride and are then allowed to react with cyclopentadiene or other 1,3-dienes. The products of cycloaddition depend on the substituents on the allenyl cations32,35. The products formed with cyclopentadiene are given in equation 14. 

The reaction of propargyl chloride 83 and trichlorosilane 84 showed two different regioselectivities depending on the choice of transition metal catalysts [88]. Whereas the Sn2 substitution proceeded to give the propargylsilane 85 with 94% selectivity using a CuCl catalyst, the silylallene 86 was obtained via an SN2 pathway with >97% selectivity with 3mol% of Ni(PhCOCHCOPh)2 (Scheme 3.42). 

The reaction could be applied to propargyl chloride 174 and propargylamine 176 and corresponding allenes 175 and 177 were obtained in 63 and 85% yields, respectively (Scheme 3.89) [126],... 

Allenyltrichlorosilanes can also be prepared by Sn2 displacement of propargylic chlorides with a Cu or Ni complex of HSiCl3 [56]. The reaction requires an amine base and a donor solvent such as THF or propionitrile (Table 9.32). Conditions can be adjusted to favor the propargylic or allenic silane, which is not isolated, but treated directly with various aldehydes to afford allenylcarbinols (A) or homopropargylic alcohols (B). These reactions presumably proceed by an SE2 pathway, such that the allenyl products arise from the propargylic silane and vice versa. 

In addition to a-allenic a-amino acids, the corresponding allenic derivatives of y-aminobutyric acid (GABA) have also been synthesized as potential inhibitors of the pyridoxal phosphate-dependent enzyme GABA-aminotransferase (Scheme 18.49) [131,138-142]. The synthesis of y-allenyl-GABA (152) and its methylated derivatives was accomplished through Crabbe reaction [131], aza-Cope rearrangement [138] and lactam allenylation [139], whereas the fluoroallene 153 was prepared by SN2 -reduc-tion of a propargylic chloride [141]. 

The boronic acid ester B was synthesized by transesterification of the corresponding pinacolester A with (lR,2R)-l,2-dicyclohexyl-l,2-dihydroxyethane. Stereoselective chlorination of B was carried out with (dichloromethyl) lithium and zinc chloride. Reaction of the obtained chloroboronic ester C with lithio 1-decyne followed by oxidation of the intermediate D with alkaline hydrogen peroxide afforded the propargylic alcohol E. Treatment with acid to saponify the tert-butyl ester moiety and to achieve ring closure, produced lactone F. Finally, Lindlar-hydrogenation provided japonilure 70 in an excellent yield and high enantiomeric purity. 

Copper(I)Chloride-Cata)ysed Reaction of Propargyl Alcohol with Propargyl Chloride in Aqueous Medium. Preparation of 4,5-Hexadien-2-yn-l-o)... 

A template mechanism was also proposed for spontaneous polymerization of propargyl chloride in the presence of poly(4-vinylpyridine). The reaction consists of partial (6-8%) alkylation of P4VPy by propargyl chloride which leads to stable complex P4VPy with monomer and then to polymerization. The product obtained contains a conjugated bond system formed by opening triple bonds in the monomer according to reaction ... 

Routes to the important class of well-defined ruthenium initiators of the Grubbs type (20b-22b) are summarized in Eigure 4 for details, see Table 2. COMC (1995) described the first example of this family, vinylalkylidene 20a, prepared by reaction of RuCl2(PPh3)3 with 2,2-diphenylcyclopropene. Subsequent treatment with PCys yields 20b (path (a)). (The corresponding complex 21a was later prepared by reaction of RuHCl(PPh3)3 with propargyl chloride see below). Initiator 20a effected controlled ROMP of and bicyclo[3.2.0]heptene M6, but ROMP of less... 

To a flask equipped with two dropping funnels and containing 2 liters of saturated sodium chloride solution, 50.0 gm (0.51 mole) of cuprous chloride, 2.0 gm of copper powder, and 50 ml of concentrated hydrochloric acid warmed to 75°C is added a 30% sodium cyanide solution until the pH approaches approximately 3-4. At this time 150.0 gm (2.0 mole) of propargyl chloride is added dropwise over a 4-hr period. At the same time, more of the aqueous 30 % sodium cyanide is added to keep the pH constant at 3-4. The reaction product is later steam-distilled from the catalyst solution, separated from the water, dried, and fractionally distilled to afford 96.0 gm (73 %), b.p. 60°-67°C (95 mm), n ° 1.44-1.45. This product is contaminated with propargyl cyanide and is refractionated to afford pure cyanoallene, b.p. 50°-51.5°C (50 mm), d° 1.4612, Amax 46,500 cm 1, emax 14,200 (methanol). 

Secondary and tertiary propargyl alcohols are directly converted to halo-allenes on reaction with concentrated aqueous hydrogen halides in the presence of the corresponding cuprous halide [60,72-73]. (See Table VII.) Better yields are obtained with hydrogen bromide. Hydrogen chloride yields chloroallene, propargyl chloride, and the chloro- 1,3-diene isomers (Eq. 60). 

Chemla and Ferreira effected lithiozincation of TMS propargyl chloride to prepare chloroal-lenylzinc bromide reagents (Table 21)33. Subsequent reaction of these reagents with N-t-butyl-substituted sulfoximines yielded the related traws-sulfoxinyl aziridines, arising from internal displacement of the chloride substituent of the anti sulfinamide adduct. A transition state in which the f-BuSO group is eclipsed with the alkynyl (vs R) substituent accounts for the preferred formation of the major A-sulfinyl diastereomer (equation 41). 

An interesting observation of the chlorination of allenes is that besides the addition products, monochlorinated compounds are also formed.252-254 Thus allene gave propargyl chloride, and tetramethylallenes gave 3-chloro-2,4-dimethyl-1,3-pentadiene. Since the reactions were carried out in the presence of oxygen, that is, under ionic conditions, proton loss from the intermediate chloronium ion or 2-chlorocarbocation explains these results. 

Addition of propargyl chlorides to l -dienes.1 The homogeneous catalyst zinc chloride-diethyl ether effects the addition of propargyl chlorides to acyclic 1,3-dienes at low temperatures. The products undergo cyclization at higher temperatures. An example is the addition of the propargyl chloride (1) to isoprene (equation I). Similar reactions are obtained on reaction of 1 with 1,3-butadiene, piperylene, and 2,3-dimethyl-1,3-butadiene. 

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