Hex- l-ene-3,4-dicarboxylate

Isolation and spectral analysis of the dimer K-crotonate (100 g) was heated at 320 °C for 4 h and subsequently treated as described above. The methyl esters (42 g), bp 100-135 °C at 6mmHg, were fractionally distilled to give three components dimethyl hex-l-ene-3,4-dicarboxylate 1, bp 97 °C at 8 mmHg dimethyl 4-methyl-pent-2-ene-3,5-dicarboxylate 2, bp 118°C at 5 mmHg dimethyl 2-metliylene-3-methylbutyl-l,4-dicarboxylate 3, bp 129 °C at 8 mmHg. 

Sodium crotonate on heating in solid state gave hex-l-ene-3,4-dicarboxylate (A). On the other hand, potassium crotonate on heating at 320 for 4 hr gives (A) along with the isomeric dimers (B) and (C) (Scheme 30). " ... 

A review containing 123 references on recent mechanistic and theoretical studies of hetero-Diels-Alder reactions has been presented. The hetero-Diels-Alder reactions of homochiral 1,2-diazabuta-1,3-dienes with diethyl azodicarboxylate are accelerated by microwave irradiation to produce the corresponding functionalized 1,2,3,6-tetrahydro-l,2,3,4-tetrazines. " The transition structures for hetero-Diels-Alder reactions involving the heteroatoms O, S, and N in dienes and also in dienophiles were determined at the MP2 and the hybrid DPT levels of theory. The activation volume of the Diels-Alder reaction between dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate and hex-l-ene indicates the conservation of all four nitrogen atoms in the transition state. " 4-n-Propyl-l,2,4-triazoline-3,5-dione reacts with cyclopentadienes, cyclohexadienes, and cycloheptadienes to yield 4 + 2-cycloadducts. ... 

The present method, based on a recent publication,8 is a modification of that previously reported.3 trans-1,2-Dihydro-phthalic acid has been converted to the cAs anhydride by heating in acetic anhydride2 which on photolysis (Hanovia, type L mercury lamp) yields the photo-anhydride, bicyclo- 2.2.0]hex-5-ene-2,3-dicarboxylic anhydride.2 4 The photo-anhydride has been converted to bicyclo[2.2.0]hexa-2,5-diene,1 bicyclo 2.2.0 hcx-2-enc,2 and cxo-bicyolo 2.2.0]hexan-2-ol2 as... 

Photoisomerization of dimethyl 4,4,6,6-tetramethyl-2,3-diazabicyclo[3.1.0]hex-2-ene-l,5-dicarboxylate generated an allyl-substituted a-diazo ester that on prolonged irradiation yielded... 

Another situation in which the chemically robust nature of the 4-methyI-l, 2,4-triazole-3,5-dione adducts has been exploited is in the synthesis of bicyclobutane derivatives.Addition of 4-methyl-l,2,4-triazole-3,5-dione to bicyclo[1.1.0]butane gave the urazole 20, which was converted to 2,3-diazabicyclo[2.1.1]hex-2-ene and by thermolysis or photolysis back to bi-cyclo[1.1.0]butane. While this is not in itself a useful synthetic sequence, the urazole intermediates in such a sequence can be chemically modified in ways that would be impossible for the bicyclobutanes themselves. Hence for the adduct 21 of dimethyl bicyclo[1.1.0]butane-l,3-dicarboxylate, the ester groups can be modified into ethyl, vinyl, substituted vinyl, hydroxymethyl, bromo and other substituents and this was used to prepare, for example, 1,3-divinylbicyclo[1.1.0]butane (22) and l-ethyl-3-vinylbicyclo[1.1.0]butane. ... 

The dibromide itself was obtained from the corresponding dicarboxylic acid by a modified Hunsdiecker reaction. This method could also be applied to the generation and trapping of highly strained cyelopropenes such as bicyclo[4.1.0]hept-l(6)-ene, bicyclo[3.1.0]hex-l(5)-ene, and tricyclo[3.2.2.0 ]non-2(4)-ene (2) which was trapped in the presence of 1,3-diphenylisoben-zofuran, although two stereoisomers of the product were reported. ... 

Cycloadditions of 3,6-bis(trifluoromethyl)-l,2,4,5-tetrazine 147 to benzocyclopropene 177 <1996ZNB348>, bicy-clo[2.1.1]hex-2-ene 178 <2003EJ0901>, and secododecahedradiene dicarboxylate 179 <2001HCA1518> gave polycyclic pyridazine derivatives 181-183. Reaction with cyclooctatetraene 180 in refluxing dichloromethane afforded 1 1 and 1 2 cycloadducts 184 and 185 (Scheme 49) <1995LA661>. 

Under a nitrogen atmosphere, dimethyl 2-cyanomethyl-2-(hex-2 -yny)malonate (3) (136 mg, 0.5 mmol) was added to a mixture of Pd(OAc)2 (5.6 mg, 0.025 mmol), 2,2 -bipyridine (4.5 mg, 0.03 mmol), HOAc (1 mL) and 1,4-dioxane (4 mL). The solution was stirred at 80 °C for 14 hours until the reaction was complete as monitored by TLC. On cooling, the reaction mixture was neutralised with saturated sodium hydrogencarbonate, and then extracted with diethyl ether (3 x 20 mL). The combined ether solution was washed with saturated sodium chloride, dried with sodium sulfate, and concentrated. The residue was purified by flash chromatography (EtOAc/petroleum ether 1/4) to give the product dimethyl 3-acetylamino-4-butyrylcyclopent-3-ene-l,l-dicarboxylate (4) in 95% yield as white solid m.p. 89.5-90.5 °C. 

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