Alkylidene malononitrile

Both butenolides 50 and 51, one tethered to an a, -unsaturated ester, the other to an unsaturated nitrile, failed to undergo cyclization. Instead, the C=C 7i-bond of the butenolide was reduced, leading cleanly and efficiently to saturation of that bond, and to compounds 54 and 55, respectively. In contrast, the corresponding alkylidene malonate 52, as well as the alkylidene malononitrile 53, both cyclize to afford a mixture of the cis-anti-cis and cis-syn-cis linearly fused lactones 56 and 57. 

Three-component reactions involving zirconocyclopentadienes have been also employed in cyclopentenone synthesis. The method combines disubstituted alkynes, isocyanates, and arylidene or alkylidene malononitriles to assemble polysubstituted cyclopentenones 171 (Scheme 8.77) [160],... 

The alkylidene malononitrile derived from chroman-4-one adds to /ra .v-P-nitrostyrcne to give (5, /< )-2-[3-(2-nitro-l-phcnylcthyl)chroman-4-ylidene]malononitrile under dihydroquinine catalysis (Scheme 39) <06OBC63> and a similar reaction of both the chromanone and thiochroman-4-one dicyanoalkenes with a,P-unsaturated aldehydes proceeds with even better ee <06CC1563>. 

Action of Carbon Disulfide on CH-Acidic Nitriles The reaction of carbon disulfide with alkylidene malononitriles (27) or alkylidene cyanoacetic acid esters (28), in dimethyl formamide in the presence of triethylamine, leads to aminodithiopyrones (29) in high yields.36,86 The preparation may also be realized directly,... 

Doubly carbonylated cyclic olefins are reactive candidates as acceptors for y-selective conjugate addition of alkylidene malononitriles. The highly... 

Scheme 33 Conjugate addition of alkylidene malononitriles as vinylogous nucleophiles...

The stereoselective vinylogous Michael addition-cyclization cascade of alkylidene malononitriles and 3-alkylideneoxindoles was effectively catalyzed by rosin-derived thiourea 36 to give spirocyclic oxindoles with excellent stereoselectivity (Scheme 35) [61]. Although simple thiourea 20 (see Scheme 16) provided low stereoselectivity (dr = 3 1, 29% ee), introduction of the rosin unit into the thiourea core significantly improved the diastereoselectivity to >20 1 the pyrrolidine structure was essential for high enantioselectivity. The effect of the chirality of the rosin component on the absolute stereocontrol was negligible and, thus, the major proposed role of this structural unit was to increase the steric hindrance of the catalyst. One of the salient features of this protocol is the... 

Scheme 34 Conjugate addition of alkylidene malononitriles to doubly activated electrophiles...

Scheme 36 y-Selective addition of alkylidene malononitriles via iminium activation... 

Scheme 37 Site-selective carbocycloaddition sequ ce of alkylidene malononitriles...

A study has been made of the asymmetric 1,4-reduction of alkylidene cyanoacetic esters and alkylidene malononitriles by chiral Grignard reagents the stereochemical results are opposite to those predicted from a cyclic mechanism (117), suggesting the alternative acyclic transition state (118) to produce the observed S -configuration in the product (Scheme 43). 

A correction has been made to the proposed structure for the product of Knoevenagel condensation of malononitrile with 2-ethoxycarbonylcyclo-hexanone. The product is not the alkylidene malononitrile (121), but is the pyridine (122), although the malonitrile (121) is definitely a precursor. 

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