H. Karlsen et al., Regiochemistry in alkylation, acylation and methoxycarbonylation of alkalisalts from 2-substituted alkenylpropanedinitriles, J CHEM S P1, (5), 2001, pp. 497-507
Alkali salts (4(-)) of several 2-substituted alkenylpropanedinitriles are p
repared, isolated and characterised by H-1 and C-13 NMR spectroscopy. By tr
eating the salt 4a(-) with 4a a dimer, 2-dicyanomethylene-6-methyl-4,6-diph
enyl-1,2,5,6-tetrahydronicotinonitrile 6, is formed, for which a single-cry
stal X-ray structure is presented. Alkylation of the ambident salts 4(-) wi
th MeX (X = I, Tf, or Br) leads to regioisomers, 1- and 3-alkylation, and c
omparison with O vs. C-alkylation of ketones is made. Double alkylation is
also observed, 3-alkylation followed by 1-alkylation. Thus from 4a(-) a mix
ture of (E)- and (Z)-2-methyl-2-(1-phenylprop-1-enyl)propanedinitrile 9b is
formed, and the X-ray structure of the former is presented. Acylation of 4
a(-) with benzoyl chloride gives only the 3-regioisomer; using equimolar am
ounts of reactants gives a ring-closure product, 2-oxo-4,6-diphenyl-2H-pyra
n-3-carbonitrile 12, while excess of benzoyl chloride gives the double-acyl
ation product, (Z)-4,4-dicyano-1,3-diphenylbuta-1,3-dienyl benzoate (Z)-13,
for which the X-ray structure is presented. Acylation of 4a(-) with acetyl
chloride gives both regioisomers; the 1-acylated product evaded isolation,
and the 3-acylation product reacted further to give the (E)- and (Z)-form
of 4,4-dicyano-1-methyl-3-phenylbuta-1,3-dienyl acetate 15. The X-ray struc
ture of the latter isomer, (Z)-15, is presented. Methoxycarbonylation of sa
lts 4(-) with methyl chloroformate gives both regioisomers, while use of me
thyl cyanoformate gives only the 3-regioisomer, in addition to a Michael ad
duct from reaction of the CN- group with protonated salt 4(-).