Ethylene substitution

In contrast to the relative lack of Diels-Alder reactivity exhibited by fluorinated ethylenes, ethylenes substituted with perfluoroalkyl groups show greatly... 

Addition of lithium derivatives of acetylenides (Li—C=C-C02R) to chiral nitrones proceeds with high stereoselectivity, giving a-acetylene substituted hydroxylamines (410a,b) (656). This reaction has been successfully applied to the synthesis of y-hydroxyamino-a, 3-ethylene substituted acids (411a,b), formed in the reduction of (410) with Zn in the presence of acid (657, 658), and to chiral 5-substituted-3-pyrroline-2-ones (412a,b) (Scheme 2.184) (658). 

Fields et alf and Schmidt made closely parallel observations concerning polar cycloaddition of ethylenes substituted at the a-position by an electron-withdrawing group and having no substituent at the jS-position. In both cases the product observed was that to be expected if the electrophile had added to the j3-carbon atom. Since it is clear that the normal ground-state polarization of acrylonitrile (127) and methyl methacrylate (128) should tend to destabilize the cation produced by j8-addition, it was concluded that the orientation of polar cycloadditions could not be predicted by the rules of electrophilic addition and that this apparent anomaly pointed toward a more concerted type of cycloaddition reaction. 

Kerr and Pauson successfully employed vinyl ester 47 as an ethylene substitute. The reaction can be carried out at ambient pressure and temperature (Equation (21)). ... 

The reactions of ethylenes substituted with fluorine and chlorine were determined by Anicich, Bowers and coworkers211-216. Su and collaborators217 tested several reactions of fluoroalkyl radical anions with C2F4 ... 

The ability to accept electrons from donors is particularly pronounced in acrylic acid derivatives [85] its alkyl esters [78, 87, 88], acrylonitrile [88], acrylamide, hydroxylacrylates [85], and further in styrenes substituted with an electronegative atom or group m-nitrostyrene, 2,6-dichlorostyrene [86], / -nitrostyrene [89] bicyclobutane-1-carbonitrile [89] lactones /J-propio-Iactone [85], sulfolactone vinyl ketones [87] unsaturated dicarboxylic acids and their derivatives diethyl fumarate, fumaronitrile [90], ROOC—N— N—COOR [86], cyclic anhydrides of diacids [91 ], particularly maleic anhydride [78, 92] ethylenes substituted with electronegative groups [93, 95]... 

Many alkyl- or aryl-substituted pyridazines (14) have been prepared by a direct one-step cyclization from an unsaturated 1,4-diketone (diacylethylene) and hydrazine. In the main symmetrically substituted diketones were employed, carrying aliphatic " or aromatic groups. Ethylene-substituted unsaturated 1,4-diketones afford tri- or tetrasubstituted pyridazines (14, R = =Rg = Rg = alkyl or aryl).2 -23 ... 

Dimethyl and 1,1-ethylene substitution brings about almost total loss of androgenic and anabolic activity. 1-Ethyl substitution in A -compounds also leads to inactivation. 

Thermodynamical Properties of Ethylenes Substituted by Heteroatoms or Functional Groups (in kcal mol"1)... 

A 6n electrocyclic closure could be implicated in the photocyclisation reaction reported for the N-amino pyridinium ion (257) and some of its ring substituted derivatives to give (258). This type of reactivity was also seen for compound (233). A summary of the previously published work and of new results for the 67t photocyclisation of photochromic ethylenes substituted by derivatives of cyclopentadiene anion and pyridinium cation has appeared.The basic skeleton involved in the rearrangement is shown in structure (259) which is in photochemical equilibrium with (260). 

Studies for various ethylenes substituted with aromatic groups of varying triplet energies revealed that a lowering in the triplet energy (E ) of the aromatic nucleus altered the mode of the isomerization from the conventional two-way isomerization to a novel one-way isomerization... 

Excess 3,3-dimethyl-l-phosphabutyne in benzene solution causes ethylene substitution in [Pt(C2H4)(PPh3)2] resulting in the following compound ... 

The structures of other adducts are assigned on the basis of analogy with these examples The tin atom is assumed to be attached to the terminal carbon atom of the carbon chain. Since this is the case for ethylenes substituted by groups with different electronic effects, such as cyano, n-hexyl, phenoxy, and 4-pyridyl, steric effects have been said to play a predominant role in determining the direction of addition (54). 

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