2- Methyl-buta-l,3-diene

Thermal cyclization of l-(l-methyl-2-pyrrolyl)buta-l,3-diene yields l-methyl-4,5-dihy-droindole (77TL151) and several examples of the cyclization of substituted vinyl derivatives have been reported, e.g. (395) -> (396) <74JCS(Pl)153l), (397) -> (398) <80JCR(S)233>, whilst the 2-(2-indolyl)propenoic ester (399) cyclizes under Vilsmeier-Haack conditions to produce (400) (80T2125). 

The analogous 2,2 -blpyridyl-[2,2-dimethyl-3-(2,2-dimethylcyclopropyl)cyclopropyl]phen-oxynickel (15) is obtained in 77% yield from a,a -bipyridyl-5-nickela-3,3,7,7-tetramethyl-exo-tricyclo[4.1.0.0. " ]heptane (13) upon treatment with phenol. Methanolysis of 15 gives a 70% yield of bi(2,2-dimethylcyclopropyl) (14). Direct acidolysis of 13 with hydrochloric acid or malonic acid is also possible and leads to the same hydrocarbon product 14 in even higher yield (91%). When 13 is treated with triphenyl phosphite at 60°C, three hydrocarbons are formed. Besides the cyclodimer 4 (3%), bi(2,2-dimethylcyclopropyl) (14, 6%) and 3-methyl-l-(2,2-dimethylcyclopropyl)buta-l,3-diene (16, 15%) have been identified. ... 

C5 H7 Cl l-chloro-2-methyl-buta-1,3-diene 35383-51-8 RI Temp/C Lambda/nm Ref. 

Recently, the research groups of Enders (Eq. 8.38)61 and Barluenga (Eq. 8.39)62 reported on the cycloaddition of chiral 2-aminobutadiene and described elegant solutions to the stereochemistry problems (regio-, diastereo-, and enantioselectivity). The reaction of 2-[(5)-2-methoxymethyl]pyrrolidin-l-yl]buta-l,3-diene with various 2-aryl-1-nitroethenes produces after hydrolysis 5-aryl-2-methyl-substituted 4-nitrocyclohexanones in excellent enantiomeric purity (ee = 75-95%) and with high diastereoselectivity (ds = 75-95%).61... 

Ab initio calculations on aza-Diels-Alder reactions of electron-deficient imines with buta-l,3-diene show that these reactions are HOMO (diene)-LUMO(dienophile)-controlled and that electron-deficient imines should be more reactive than alkyl-or aryl-imines. The Diels-Alder reaction of r-butyl 2//-azirine-3-carboxylate (80) proceeds with high diastereoselectivity with electron-rich dienes (81) (Scheme 28). The hetero-Diels-Alder additions of imines with sterically demanding dienes yield perhydroquinolines bearing an angular methyl group. The asymmetric hetero-Diels-Alder reaction between alkenyloxazolines and isocyanates produces diastereometri-cally pure oxazolo[3,2-c]pyrimidines. °... 

The chalcogene heterocycles have been used as stable precursors for sulfur-and selenium-containing hetero-l,3-dienes in cycloaddition reactions 3//-1,2,4-Thiaselenazoles are a convenient source of 4,4-bis(trifluoromethyl)-l-thia-3-aza-buta-l,3-dienes, and 3H-diselenazoles are a convenient source of 4,4-bis(trifluoromethyl)-l-selena-3-azabuta-l,3-dienes as well as bis(tnfluoro-methyl)-subsbtuted mtnle ylides [137]... 

Molander and Siedem have reported the reaction of l-methoxy-l,3-bis(trimethylsilylo-xy)-buta-l,3-diene, the bis(trimethylsilyl) enol ether of methyl acetoacetate, with 1,4- and 1,5-dicarbonyl species under the influence of trimethylsilyl triflate. Two regioisomeric oxabicyclo[3.2.1]octane products are formed (Scheme 83)194. Use of 4- or 5-ketoacyl silanes as the dicarbonyl species can result in a reversal of the sense of regioselectivity. 

Trifluoroethyl 2-(trifluoromethyI)prop-2-enoate reacts with various dienes to provide cycloadducts in high yields. A typical example is the reaction with ( )-l-methoxy-2-methyl-3-(trimethylsiloxy)buta-l,3-diene leading to the trifluoromethyl-substituted cyclohexenone 13 which was used as a precursor of 16,16,16-trifluororetinal." The reaction has also been performed with a chiral dienophile."... 

To a solution of ( )-1-methoxy-2-methyl-3-(trimethylsiloxy)buta-l,3-diene (lOg, 54mmol) in CIljClj (25 mL) was added a solution of 2,2.2-trifluoroethyl 2-(trifluoromethyl)acrylate (11.8g, 54mmol) in CH2CI2 (15mL) at 0 C under argon, and the solution was stirred for 3 min. After evaporation of the solvent, MeOH (30 mL) and TsOH (2 g, 10.5 mmol) were added at 0 C. The resulting solution was stirred at the same temperature for 1.5 h. F.vaporation of the solvent and vacuum distillation of the residue gave 13 yield 16.5 g (87%) bp 88 C/3 Torr. 

Buta-1,3-diene, 1 -(2 -furyl)-pyrolysis, 4, 600 Buta-1,3-diene, 1-mercapto-thiophenes from, 4, 887 Buta-1,3-diene, 1 -(1 -methyl-2-pyrrolyl)-thermal cyclization, 4, 285 Buta-l,3-diene, l-(2-thienyl)-electrocyclization, 4, 748 Butadienes... 

In vfc-dihalocyclopropanes with two different halogens, the bond opposite to the better leaving group is opened. For example, 2-bromo-l,l-dichloro-3,3-dimethylcyclo-propane undergoes rearrangement in quinoline at 160°C to give l,l-dichloro-3-methyl-buta-1,3-diene in 64% yield. ... 

The formation of 2-vinylindene and 8,9-dihydro-5//-benzocycloheptatriene during the Diels-Alder addition of buta-1,3-diene to benzocyclopropene was discussed in Section 2.4.1.. The products are ascribed to trapping by the diene of a diradical, derived from benzocyclopropene. A diradical mechanism has also been invoked for the rationalization of the formation of the stereoisomeric 2-vinyl-2,3-dihydro-l//-indenes 3 from methyl 1-methylbenzocyclopropene-l-carboxylate or 1-methylbenzocyclopropene-l-carbonitrile and buta-l,3-diene. The same mechanism should apply in the formation of the unsymmetrical adduct of benzocyclopropene with 1,3-diphenylisobenzofuran (Section 2.4.1.). ... 

Only a few examples are known of reactions which involve isomeric (buta-l,3-dien-2-yl)phosphonic derivatives. The course of chlorination of the esters 403 depends on the nature of the substituent R when the latter is hydrogen, classical 1,4-addition of halogen can be followed by EtjN-promoted dehydrohalogenation to give the esters 404, but when R is methyl (i.e. the diene terminal carbon is tertiary), the result is the formation of the 1,2-oxaphosph(V)ol-3-ene 405, the outcome being dependent, presumably, on the stability of an intermediate carbocation. ... 

Pfaltz and his coworkers (Fritschi et al., 1986, 1988a, 1988b Pfaltz, 1989, 1993) used the semicorrin-copper complex 8.160 and the corresponding 2 1 complex 8.162 as a reagent for cyclopropanation of styrene, buta-l,3-diene, 1-methyl-penta-2,4-diene, and hept-l-ene (8-71). The yield and the enantiomeric excess found for the two products are shown in Table 8-2. 

Diels-Alder Cycloadditions.—The range of functionalized diene systems, displaying regioselective behaviour in the Diels-Alder reaction, continues to expand. Notable new additions include l-phenylseleno-2-trimethylsilyloxy-4-methoxybuta-l,3-diene (82) and the isomers 1- and 2-methyl-l,3-bis(trimethylsilyloxy)buta-l,3-dienes (84) and (85). The diene (82) is readily derived from l-methoxy-3-trimethylsilyloxybuta-1,3-diene (81) and provides a direct route to the synthetically valuable 4-acylcyclohexa-2,5-dienones (83), whereas dienes (84) and (85) react with activated dienophiles (e.g. RCH=CHC02Et) in good yield, leading to keto-esters of the type (86) on hydrolysis. 

Effective routes to buta-l,3-diene-l,l,4-tricarboxylic acids and to derivatives of (2Z,4Z)-3-methylhexa-2,4-dienedioic acid have been reported. Five different 6-substituted (Z)-2-en-4-ynoic acids have been synthesized, mainly by the coupling of methyl (Z)-3-iodopropenoate and the appropriate cuprous acetylide followed by hydrolysis of the ester. A synthesis of racemic integerrinecic acid (31), in five steps from ethyl acrylate, is reported. ... 

Other examples where the intramolecular variant has been employed include the direct formation of bridgehead bicyclo[3,n,l]alkenes from 2-(alkenyl)buta-1,3-dienes and the preparation of rrans-perhydronaphthalenes, bearing an angular methyl group, from acyclic trienes. ... 

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