2-Cyano-azadiene Diels-Alder reaction

Similarly, Motorina described the intramolecular hetero-Diels-Alder reaction of N-alkyl-2-cyano-l-azadienes 86 (Scheme 9.26) [76] although the reaction had already been performed by heating the reactants in benzene overnight in a sealed tube at 110 °C, it was found that reaction time could be reduced to 14 min in a microwave oven at 650 W. 

Ab initio and density functional theoretical studies of the 4 + 2-cycloaddition of 2-azabutadiene with formaldehyde predict a concerted reaction that agrees well with experimental evidence.184 The azadiene A-plienyl-l-aza-2-cyanobuta-l,3-diene reacts with electron-rich, electron-poor, and neutral dipolarophiles under mild thermal conditions.185 5,6-Diliydro-4//-1,2-oxazines have been shown to be usefiil as synthon equivalents of 2-cyano-l-azabuta-1,3-dienes.186 The intramolecular Diels-Alder reaction of 1-aza-l,3-butadienes (106) can be activated by a 2-cyano substituent (Scheme 37).187 Stereoselectivity in the hetero-Diels-Alder reactions of heterobutadienes, nitrosoalkenes, and heterodienophiles has been extensively reviewed.188 The azadiene l-(f-butyldimethylsilyloxy)-l-azabuta-1,3 -diene (107) reacts with halobenzo-quinones, naphthoquinones, and A-phcnylmalcimidc to yield low to good yields of various pyridine heterocycles (108) (Scheme 38).189 The 4 + 2-cycloaddition of homophthalic anhydride with A-(cinnamylidcnc)tritylaminc produces the 3,4-adduct whereas with A -(cinnamylidcnc)bcnzylidinc the 1,2-adduct is produced.190... 

Intramolecular Diels-Alder reactions of azadienes 76 afforded 6-cyano-2,3,4,8,9,9a-hexahydropyrido[2,l-6][l,3]oxazines 77 (99TL7211, 99TL7215). Cyclization was carried out smoothly at or below room temperature in... 

Predict the regioselectivity in the Diels-Alder reactions of acrolein and N-acetyl-2-cyano-4-phenyl-l-azabutadiene with 1-hexene, styrene, ethyl vinyl ether and methyl acrylate. The FOs of the azadiene are given below the others may be found in the Appendix. 

Bi(OTf)3, cyclic epoxides also react with amines, Me3SiN3, and Me3SiCl to afford the corresponding a-functionalized alcohols (Equation (82)).138,138a BiCl3 and Bi(OTf)3 catalyze aza-Diels-Alder reactions of A-arylimines with both Danishefsky s diene and dienophiles (Equation (83))139 and the intramolecular aza-Diels-Alder reaction of A-vinyloxypropyl-2-cyano-l-azadienes (Equation (84)).140... 

Af-Acyl-2-cyano-l-azadiene is sufficiently stable for its properties and reactions to be studied. It is a low-melting solid which reacts with the relatively weak dienophile norbomene in a Diels-Alder fashion [B-42] in boiling benzene over 7 h to give one main product and two minor stereoisomers of it [3853]. Similar reactions occur with the V. -dimethylhydrazone of 2-methylacrolein and 1,4-naphthoquinone or its pyridine analogue. In some of these cyclizations, there is good steroselectivity but in others, a mixture of positional isomers is formed [3279]. A Diels-Alder reaction of 2-azabuta-1,3-diene which carries the easily eliminated dimethylamino groups is a convenient route to an azacarboline [3108]. 

Intramolecular Diels Alder reaction of the 2-cyano-substituted A-alkyl azadiene 221 to indolizidine 222 (70%) was carried out under MWI within 14 min (Scheme 47). This conversion took place on heating in benzene overnight in a sealed tube to give a 90% yield (97JOC2098). 

Lewis acids such as Cu(OTf)2, its chiral bisoxazoline complex Cu(oxaz)2(OTf)2, and BiCls catalyze the intramolecular Diels-Alder reaction of 1-azadienes (eq 21). The 2-cyano-l-azadienes (4), containing an electron rich enol ether dienophile component, undergo cycloaddition to give the oxazinopiperidines (5) in 59-80% yield. o... 

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