Cis-l,4-Dichloro-2-butene

Chemical Designations - Synonyms 1,4-Dichloro-2-butene 2-Butylene Dichloride 1,4-Dichloro-2-butylene cis-l,4-Dichloro-2-butene trans-l,4-Dichloro-2-butene Chemical Formula C1CHjCH=CHCH2C1. 

Volume 75 concludes with six procedures for the preparation of valuable building blocks. The first, 6,7-DIHYDROCYCLOPENTA-l,3-DIOXIN-5(4H)-ONE, serves as an effective /3-keto vinyl cation equivalent when subjected to reductive and alkylative 1,3-carbonyl transpositions. 3-CYCLOPENTENE-l-CARBOXYLIC ACID, the second procedure in this series, is prepared via the reaction of dimethyl malonate and cis-l,4-dichloro-2-butene, followed by hydrolysis and decarboxylation. The use of tetrahaloarenes as diaryne equivalents for the potential construction of molecular belts, collars, and strips is demonstrated with the preparation of anti- and syn-l,4,5,8-TETRAHYDROANTHRACENE 1,4 5,8-DIEPOXIDES. Also of potential interest to the organic materials community is 8,8-DICYANOHEPTAFULVENE, prepared by the condensation of cycloheptatrienylium tetrafluoroborate with bromomalononitrile. The preparation of 2-PHENYL-l-PYRROLINE, an important heterocycle for the synthesis of a variety of alkaloids and pyrroloisoquinoline antidepressants, illustrates the utility of the inexpensive N-vinylpyrrolidin-2-one as an effective 3-aminopropyl carbanion equivalent. The final preparation in Volume 75, cis-4a(S), 8a(R)-PERHYDRO-6(2H)-ISOQUINOLINONES, il lustrates the conversion of quinine via oxidative degradation to meroquinene esters that are subsequently cyclized to N-acylated cis-perhydroisoquinolones and as such represent attractive building blocks now readily available in the pool of chiral substrates. 

Dimethyl malonate (200 mmol) was dissolved in 300 ml DMF, cooled to 0 °C, and lithium hydride (500 mmol) added in one portion. To the cooled mixture was slowly added cis-l,4-dichloro-2-butene (228 mmol) and the mixture stirred 72 hours. Thereafter, the mixture was diluted with 500 ml 20% diethyl ether/hexanes then poured into 350 ml cold water. After washing with 300 apiece water and brine, the product was isolated in 50% yield, mp = 63.4 °C. H-NMR and IR data supplied. 

Ma.nufa.cture. Butenediol is manufactured by partial hydrogenation of butynediol. Although suitable conditions can lead to either cis or trans isomers (111), the commercial product contains almost exclusively iVj -2-butene-l,4-diol Trans isomer, available at one time by hydrolysis of l,4-dichloro-2-butene, is unsuitable for the major uses of butenediol involving Diels-Alder reactions. The Hquid-phase heat of hydrogenation of butynediol to butenediol is 156 kj/mol (37.28 kcal/mol) (112). 

Hydrochlorination of 1,3-Butadiene. A historic process for the synthesis of adi-ponitrile was the transformation of 1,3-butadiene through 1,4-dichlorobutene.187 Addition of HC1 was carried out in the vapor phase (125-230° C) in an excess of 1,3-butadiene. A mixture of isomeric dichlorobutenes (3,4-dichloro-l-butene, cis-and trans-l,4-dichloro-2-butene) was formed. They underwent further transformations to form the dicyanides and then, after hydrogenation, to give adiponitrile. 

Racemic baikiain can be obtained by an electrolytic reduction of picolinic acid60 (see Section II, B, 2), by an eight-step synthesis from l-benzoyloxy-4-bromo-2-butyne163 or, more simply, from cis-1,4-dichloro-2-butene (175).164... 

The introduction of substituents at positions 1 and 2 of a pyrrolo[l,2-a]-indole derivative was investigated by the approach shown in Scheme 18. Compound 110 was condensed with Z-l,4-dichloro-2-butene to give a pyrroline, which afforded 131 on treatment with benzaldehyde and NaOH. Thermal isomerization produced 9,9a-dihydro-3H-pyrrolo[l,2-a]indole 132. Osmium tetroxide then converted 132 into cis-diol 133 [47]. 

Antimony(V) chloride (Sbaj) " and molybdenum(V) chloride (M0CI5) can react spontaneously with alkenes to give predominantly the corresponding ci s-1,2-dichlorides (equation 11). The reaction probably proceeds through a successive insertion and reductive elimination sequence, llie chlorination of butadiene with SbClj and copper(II) chloride results preferentially in the formation of (Z)- and ( )-1,4-dichloro adducts, while the reaction with chlorine gives an 1 1 mixture of 1,2- and 1,4-adducts, as shown in Table 2 and equation (12). The formation of (Z)-l,4-dichloro-2-butene may be ascribed to a transition state as shown in Scheme 3. 

What term does describe the polymerization of isoprene to cis-1,4-polyisoprene Here we quote further from Eliel (1962). Stereoselective, in contrast, simply means that, of two (or more) possible stereoisomeric products in a reaction, one is produced in predominance (usually in great predominance) over all the others. An example is the 1,4 addition of chlorine to butadiene reported by Mislow and Heilman (1951). The product is only ira is-l,4-dichloro-2-butene (IX). Another example of a ster-... 

Another example is the vapor-phase chlorination of butadiene, which gives a mixture of dichlorobutenes of which 3,4-dichloro-l-butene (12) is the only desired isomer for the chloroprene synthesis [23, 24] (cf. eq. (14)). It is easily boiled off from the cis/trans 1,4-dichloro-2-butenes (123 vs. 155 °C). The migratory isomerization of residual 1,4-isomers 11 is effected by Cu complexes and seems to operate through -olefin/ -allyl intermediates. The chloride probably migrates via the copper center, but no mechanistic details are available. 

The route to the cis-enediyne 32 a starts from cis-2,3-dichloro-2-buten-l,4-diol, which is obtained by exhaustive reduction of mucochloric acid (Scheme 13-8) [45]. The two dibromo-methylene residues in 36, the direct precursor to 32 a, are introduced sequentially in a synthetic route which includes as the key step the selective reduction of orthoester 33 to the monopro-tected diol 34. Since compound 35 and all other intermediates with dibromomethylene groups... 

Cyclobutenes. Ethereal cis-1,4-dichloro-l,2-diphenyl-1-butene added to pure sublimed Mg, 1,2-dibromoethane added as activator, and the product isolated after 19 hrs. 1,2-diphenyl-1-cyclobutene. Y 86%. — This synthesis is sensitive to the structure of the dichloride and to experimental conditions. F. e. s. M. S. Newman and G. Kaugars, J. Org. Ghem. 30, 3295 (1965). 

CTFE dimers can be produced catalytically and thermally to produce 4,4-dichlorohexafluoro-l -butene. The catalyst of the reaction is sintered porous polytet-rafluoroethylene or a mixture of PTFE and sodium or potassium fluoride at 300—450°C.f The dimer yield of the reaction is usually very high (>90%). The rest of the CTFE is converted to trimers. Thermally CTFE dimerizes to a mixture of cis- and ra 5-l, 2-dichloro-hexafluorocyclobutanes.t 1... 

---