Dichloro-2-butyne

Dibenzoy loxy-7 a, 8a-methylen-5a,8a-androstan-6a-ol, 113 Dibromocarbene, 366, 367, 372 1,4-Dichloro-2-butyne, 68 Dichlorocarbene, 364 9a,l 1 -Dichloroandrosta-1,4-diene-3,17-dione, 150... 

Double 1,6-dehydrochlorination of I,6-dichloro-2,4-hexadiyne, analogous to the formation of butadiyne from 1,4-dichloro-2-butyne and strongly basic reagents, was described for the first time by Bohlmann and Jones et al. [147]. The extremely unstable 1,3,5-hexatriyne was obtained in a moderate yield as a dilute solution in an organic solvent. 

Transfer the supernatant, from step 2, by cannula, to the CuCN/LiBr solution at -20°C. Stir the solution for 15 min, and then warm to 0°C. Add 1,4-dichloro-2-butyne (1.84 g, 15 mmol). Stir the solution for 30 min, and then at room temperature for 1 h. 

Since the exocyclic sulfur is more reactive in the ambident anion than in A-4-thiazoline-2-thione. greater nucleophilic reactivity is to be expected. Thus a large variety of thioethers were prepared in good yields starting from alkylhalides (e.g.. Scheme 38 (54, 91, 111, 166-179). lactones (54, 160), aryl halides (54, 152. 180, 181), acyl chlorides (54. 149, 182-184), halothiazoles (54, 185-190), a-haloesters (149. 152. 177. 191-194), cyanuric chloride (151). N.N-dimethylthiocarbamoyl chloride (151, 152, 195. 196), /3-chloroethyl ester of acrylic acid (197). 3-dimethylaminoethyl chloride (152). 1.4-dichloro-2-butyne (152), 1,4-dichloro-2-butene (152). and 2-chloro-propionitrile (152). A general... 

DisubstUuted butadienes,2 2,3-Bis(trimethylstannyl)-1,3-butadiene (1) can be prepared by reaction of 2,3-dichlorobutadiene or 1,4-dichloro-2-butyne with 2 equiv. of trimethylstannyllithium (equation I). 2,3-Disubstituted butadienes can be prepared from 1 in one step by reaction of the dianion formed with methyllithium at - 78° with 2 equiv. 

Zero-valent nickel complexes are known to reduce 1,2-dihalides to olefins and to mediate C,C-coupling reactions of vinyl halides. Based on these facts, lyoda and coworkers developed a two-step, one-pot synthesis of alkyl-substituted [4]radialenes which starts from 2,3-dihalo-l,3-butadienes and 1,4-dichloro-2-butyne derivatives and circumvents the isolation of the butadiene intermediates. Furthermore, the synthesis can be made catalytic in nickel when the Ni(0) complex is generated from NiBr2(PPh3)2 with a more than stoichiometric quantity (based on the dihalide) of zinc. Again, the formation of radialene 94 must compete with that of 95 and 96. With preformed Ni(PPh3)4 and Ni(PBu3)4, the [4]radialene is normally favored in benzene solution, but formation of 95 and/or 96 becomes important in the more polar solvents THF and DMF. With a catalyst... 

Preparation. A simple route to this reagent is by reaction of 1,4-dichloro-2-butyne x ith Bu SnLi. Note that coupling of l,3-butadien-2-ylmagnesium chloride with Ph,SnCl leads to the triphenyl analogue but the coupling with BujSnCl proceeds without skeletal -hange. 

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