This paper is dedicated to Projessor Ross Stewart on the occasion of his 65th birthdayMIROSLAW DWORNICZAK and KENNETH T. LEFFEK. Can. J. Chem. 68, 1657 (1990).3,3,6,9,9-Pentamethyl-2,1O-diazabicyclo[4.4.0]dec-l-ene has been synthesized and its proton transfer reactions, together with those of the bases 2,2,6,6-tetramethylpiperidine and 1,2,2,6,6-pentamethylpiperidine, have been studied with the carbon acids 4-nitrophenylphenylcyanomethane and 2-methyl-4-nitrophenylphenylcyanomethane. Equilibrium constants, rate constants, primary deuterium isotope effects, and activation parameters are reported for the reactions in acetonitrile solvent. Values of the pK, in acetonitrile have been measured for the conjugate acid of each base and the Bronsted (3 value of 0.56 in acetonitrile has been determined for the proton transfer from 4-nitrophenylphenylcyanomethane.

The kinetics of the reaction of 1,1,1 -trifluoro-2,2-bis-(4-nitropheny1)ethane with piperidine and pyrrolidine bases in a series of solvents [acetonitrile (MeCN), benzonitrile (PhCN), and dimethyl sulphoxide (Me,SO)] are reported. The reaction is complex, leading to a 1 -amino-1 -fluoro-2,2-bis-(4-nitropheny1)ethene as the final product via the intermediate 1,l -difluoro-2,2-bis-(4-nitropheny1)ethene. The reaction is promoted only by primary and secondary amines; tertiary amines appear to be inactive even under reflux conditions. The entropies of activation (ASX/J mol-' K-l) are negative and large ( -183.7 and -162.3) for the reaction with piperidine in PhCN and MeCN; for reaction in Me,SO the value is only -77.4. The kinetic isotope effects (k,/k,) fall between 1 .O and 1.6 at 30 "C. The results obtained are discussed in terms of a multistep mechanism, (€1 C B ) , ~, consisting of a pre-equilibrium followed by fast addition-elimination steps.

Die nucleophile Substitution der Trihalogenpyrimidine (I) mit den Aminen (II) erfolgt regioselektiv in 4‐Stellung zu den Aminen (III); als Nebenprodukte fallen in geringen Ausb. die Isomeren (IV) an.

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ChemInform Abstract (prim. deuterium kinetic isotope effects: 4.2-5.5; activation parameters).