The Introduction of Substituted Vinyl Groups. VII. Alkylidene and Substituted Vinyl Alkylmalononitriles

supporting

confidence: 60%

The Structure of Cyclohexylidenemalononitrile Dimer

Weir¹,

Hyne²

1963

“…Hence the linear structure can be ruled out. The presence of these two quartets likewise rules out structure I11 (6).…”

Section: -Pentylidenemalononitrilementioning

confidence: 91%

“…The preparatioil of a,p-unsaturated dinitriles of the type R?C=C(CN)2 by basecatalyzed condensatioil of the corresponding carbonyl compound (R2C=O) with malononitrile has been the subject of investigation from the time of I-Ieucli oinvards (1)(2)(3)(4)(5)(6)(7)(8)(9). In addition to the expected unsaturated dinitrile, however, a second substance, considered to be a diiner of the dinitrile, has been isolated in several instances ( 5 ) .…”

mentioning

confidence: 99%

See 1 more Smart Citation

Base-Catalyzed Dimerizations of Alkylidenemalononitriles

Weir¹,

Hyne²

1964

The base-catalyzed dimerizations of several all;~liclenemalo~~o~~itriles have been studied, and proton 11~1clear magnetic resonance (n.m.r.) spectral evidence is presented in support of the s~~ggested cyclic structures of these dimers.The preparatioil of a,p-unsaturated dinitriles of the type R?C=C(CN)2 by basecatalyzed condensatioil of the corresponding carbonyl compound (R2C=O) with malononitrile has been the subject of investigation from the time of I-Ieucli oinvards (1-9). In addition to the expected unsaturated dinitrile, however, a second substance, considered to be a diiner of the dinitrile, has been isolated in several instances ( 5 ) . The formation of this dimeric product has previously led to confusion about the nature of the inonorneric product. For example, cyclol~exylidene~~~alononitrile (5) and isopropylidenemalononitrile (4) were originally reported to be crystalline solids and it ulas later sholvn (6) that they are, in fact, liquids.These crystalline products are obtained in varying yields froin the base-catalyzed condensations of both aromatic and aliphatic ketones with malononitrile. T h e structures of sonle of theill have recently been investigated (7,8,9). Thus, Anderson, Bell, and Duncan (7) studied the solid products obtained froill the base-catalyzed reactions of malononitrile with several carbonyl conlpounds including acetone, acetophenone, and benzil. They suggested, largely on the basis of infrared spectral analysis, that the structure of the dimer of isopropylidenemalononitrile was linear (lIe2C=C(CN) .C(SH2)=CI-I .C4Ie =C(CbQ2). Williams later investigated seine of the reactions of this diiller and concluded that it was cyclic (see Chart A (Ia)(Ic)). In a recent communication (9) we have suggested that the dimer of cyclol~ex~~lidenemalononitrile is likewise cjiclic.We have now investigated the base-catalyzed diit~erizations of other all;ylidenemalononitriles in an attempt to determine whether or not the formation of cyclic diniers can be considered to be a general reaction of these conlpounds. The proton i1.m.r. spectral evidence which we have obtained leaves little doubt that the diillers are cyclic, but they appear to differ froill isopropylidenemalonoi~itrile diimer in the location of the carbon-carbon double bond.The mechanism for cyclic ditller formation proposed for isoprop)-lidenemalononitrile by Williams (8) can be expanded into the general forill shown in Chart A. Compounds I in Chart A represent the reaction sequence for isopropylidenemalononitrile itself. Compounds 11, 111, and IV represent the three other all

“…The reactive nature of methylenemalononitrile systems of the type RlR2C=C(CN)2 in the presence of base has been known for some time (1,2). In particular the tendency of such compounds to undergo condensations and dimerizations in the presence of base has been the subject of several recent investigations (3)(4)(5)(6)(7).…”

Section: Introductionmentioning

confidence: 99%

SOME BASE-CATALYZED CONDENSATIONS OF SYSTEMS OF THE FORM R₁R₂C=C(CN)₂

Weir¹,

Hyne²

1965

We have investigated the condensations of the systems +CI43C=C(Ci\r)Z, 4HC=C(CN)?, and CH3HC=C(CPi)2 in the presence of organic bases. Proton nuclear magnetic resonance (n.m.r.) speEtral evidence is presented in support of the suggested structures of the condensation products, and an attempt has been made to present diagrammatically the interrelation between these condensations and other known reaction pathways for condensations of this type.