1.4- Dicyano-l,3-dienes

Cuprous chloride/oxygen 1,4-Dicyano-l,3-dienes from o-diamines... 

With conjugated dienes competitive [4 + 2] cycloaddition occurs and often is the predominant pathway. However, 1,1-diarylbuta-l,3-dienes react with l,l-dicyano-2,2-bis(trifluoromethyl)-ethenc to give the [2 -I- 2] adducts as the major products,39... 

In order to make these oxidative reactions of 1,3-dienes catalytic, several reoxidants are used. In general, a stoichiometric amount of benzoquinone is used. Furthermore, Fe-phthalocyanine complex or Co-salen complex is used to reoxidize hydroquinone to benzoquinone. Also, it was found that the reaction is faster and stereoselectivity is higher when (phenylsulflnyl)benzoquinone (383) is used owing to coordination of the sulfinyl group to Pd, Thus the reaction can be carried out using catalytic amounts of PdfOAcji and (arylsulfinyl)benzoquinone in the presence of the Fe or Co complex under an oxygen atmosphere[320]. Oxidative dicyanation of butadiene takes place to give l,4-dicyano-2-butene(384) (40%) and l,2-dicyano-3-butene (385)[32l]. 

Unsymmetrical dienes in this synthesis are often capable of high regioselectivity (eqs. 4 and 5) (82). Reaction of (81) with 2-methoxycarbonyl-l,4-ben2oquinone [3958-79-0] yields 97% of (82) [80328-15-0]. Reaction of (81) with 2,3-dicyano-l,4-ben2oquinone [4622-04-2] yields 58% of (83) [80328-16-1]. 

Photocycloaddition of 2-alkoxy-3-cyanopyridines with methylacrylonitrile yields a bicyclic [2+2] cycloadduct intermediate followed by rearrangement to give 368 in 44—55% yield along with 3-acetyl-4-amino-l,5-dicyano-2,5-dimethylcyclohexa-1,3-diene (15-17%). Equimolar quantities of reagents have to be used for the formation of 368... 

N-Substituted 1,2-diazocine 34, containing a conjugated diene moiety, was reacted with dimethyl acetylenedicar-boxylate (DMAD) to give the cycloaddition adduct 35 in excellent yield. The latter was oxidized with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) to give the benzodiazocine 36 (Scheme 7) <2004TL3757>. 

The most frequently encountered examples of the first type are the addition of diazoalkanes to 3//-pyrazoles (or addition of two moles of diazoalkane to an acetylene). For example, in the reaction of 2-diazopropane with dimethyl butynedioate, addition of one mole of 2-diazo-propane generated dimethyl 3,3-dimethyl-3/f-pyrazole-4,5-dicarboxylate (1), and addition of a second mole of 2-diazopropane gave dimethyl 4,4,8,8-tetramethyl-2,3,6,7-tetraazabicy-clo[3.3.0]octa-2,6-diene-l,5-dicarboxylate (2) which on photolysis (not thermolysis or sensitized photolysis ) gave a 41% yield of dimethyl 2,2,4,4-tetramethylbicyclo[1.1.0]bu-tane-l,3-dicarboxylate (3). Similar bis-additions are known for dicyano-, diacetyl-, and diben-zoylacetylene, but only the dicyano system gives the bicyclobutane on thermal deazetization. ... 

A propellene has been converted to a conjugated propelladiene 10,10-dibromo[4.3.1]pro-pell-3-ene reacted with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone to give 10,10-dibro-mo[4.3.l]propella-2,4-diene in 35 /o yield. -... 

A crystalline film of 314 mg (0.744 mmol) of l,l,3,3-tetraphenyl-5,5-dicyano-1,4-pentadiene 1 a, deposited by slow evaporation of a 20% ether in hexane solution, was irradiated at 78 °C for 2.5 h through Pyrex. The resulting orange-red solid was subjected to preparative HPLC eluted with 8% ether and 0.5% acetonitrile in hexane to give 227.1 mg (72.3%) of starting diene and 74.8 mg (23.8%) of 2 a as a pale purple-red solid. Recrystallization from ether-hexane yielded 69.7 mg (21.6%) of 2a as a white solid (mp 125-128°C). 

Upon UV irradiation of dicyano(pyridinio-5,6 or pyridazinio7)methanide, dicyanocarbene was generated, which then reacted with benzene to give bicyclo[4.1.0]hepta-2,4-diene-7,7-dicarboni-trile (2)5,7 or with (Z)-4-methylpent-2-ene nonstereospecifically to give cis- and trans-2-iso-propyl-3-methylcyclopropane-l,l-dicarbonitrile.6 However, due to competing photoreactions of the ylide, the carbene-transfer reaction is not efficient and the cyclopropanes were ohtained in poor yield only.5... 

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