L,4-Dichloro-2-butyne

Since the exocyclic sulfur is more reactive in the ambident anion than in A-4-thiazoIine-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). fV.N-dimethylthiocarbamoyl chloride (151, 152. 195. 196), /3-chloroethyl ester of acrylic acid (197), (3-dimethylaminoethyl chloride (152). l,4-dichloro-2-butyne (152), 1,4-dichloro-2-butene (152), and 2-chloro-propionitrile (152). A general... 

In a deceivingly simple process apparently involving a butatriene intermediate, a one-pot preparation of ethyl 5-methylpyrrole-2-carboxylate (6) from diethyl acetamidomalonate (4) and l,4-dichloro-2-butyne (5) has been described <96JOC9068>. 

Thieno[3,4- ] and [3,4-f]pyridine derivatives can be generated from a cycloaddition reaction of oxazinones with l,4-dichloro-2-butyne to afford polyhalogenated pyridine products which cyclize to thienopyridines (Scheme 39) <2001T4203>. In a similar reaction, pyrazinones, 122, containing alkynyl substituents cyclize to form thieno[3,4-3] and [3,4-i ]pyridine derivatives <2002TL799, 2004T429>. 

American workers needed to prepare the bis-amino acid 1 and adopted a literature procedure in which two equivalents of diethyl acetamidomalonate were to be alkylated with one equivalent of l,4-dichloro-2-butyne using two equivalents of sodium ethoxide in hot ethanol. Hydrolysis and decarboxylation of the dialkylated malonate would then give 1. This alkylation reaction was carried out, but ten equivalents of sodium ethoxide were used rather than two. This resulted in formation of ethyl 5-methylpyrrole-2-carboxylate in ca. 40% yield. Further study showed that the reaction to produce the pyrrole required equimolar amounts of the acetamidomalonate and the dichlorobutyne, excess of sodium ethoxide, and heating. No pyrrole was formed at room temperature. 

Heating of diethyl acetamidomalonate 508 with l,4-dichloro-2-butyne 509 in the presence of an excess of sodium ethoxide gave the pyrrole 510 (Equation 140), possibly via the intermediacy of a butatriene intermediate <1996JOG9068>. 

Isoxazolidin-3-one 334, prepared by catalytic hydrogenolysis of 3-(benzyloxy)-4,5-dihydroisoxazole, reacted with l,4-dichloro-2-butyne in refluxing acetone in the presence of K2CO3 to give a 4 1 mixture of the regioisomeric N- and 0-alkyl derivatives (Scheme 82) <1999BMC1539>. 

For example, the treatment of l,4-dichloro-2-butyne with sodium hydroxide results in diacetylene (HC=C—C CH) in good yield (see Table 4, entry 39). 

The recent development of dienes incorporating latent has greatly expanded the utility of Diels Alder approaches of complex molecules. Butadiene substituted by silicon at is available from l,4-dichloro-2-butyne by H2PtCl2catalyzed reaction with Et3SiH followed by dehydrohalogenation (Zn). The product reacts readily with dlenophiles. ... 

Lithium 4,4 -di-t-butylbiphenylide (LDTBB). 13, 162-163 16, 195-196 17, 164 Lithium-halogen exchange. The reagent has been proven particularly effective for chloro compounds, as shown in the Barbier-type reactions involving chloromethyl ethyl ether, l,4-dichloro-2-butyne and -2-butenes. Vinylic chlorides also readily undergo exchange, and actually 2,3-dichloropropene is converted to the dilithio reagent. ... 

We also found it possible to make 2,3-disubstituted-1,3-butadienes using CuCN LiBr and cross-coupling with l,4-dichloro-2-butyne. This reaction was... 

---