The subject of this work is the study of a new type of radical polymerization that occurs at elevated temperatures (80-100 ° C) in mixtures of acrylates or (meth)acrylates and imine baes (IBA polymerization). The radical character of this polymerization is proven by the determination of copolymerization ratios and the reaction kinetics. On the basis of these facts and the hypothesis that the vinyl monomer acts as a co-initiator, calculations reveal the concentration of the initiating species to be very low ( K eq < 10 − 6 ). Furthermore, the choice of the reaction medium plays a crucial role on reaction kinetics and the average molecular weight of the resulting polymer. In combination with computational methodologies on the initiation, the multistep nature of this reaction is indicated. Scheme 1 . Suitable imine bases for a radical formation with (meth)acrylates and tertiary amine bases, which cannot be used such as DABCO and DMAP.Scheme 2 . Proposed multistep mechanism for the IBA polymerization initiation. The educts, the zwitterionic intermediate, and the six-membered ring are labeled as Ed , ZW , and Pr , respectively.

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Second-order rate constants (k) of the reactions of various barbiturate anions such as the parent barbiturate, 1,3-dimethylbarbiturate, 2-thiobarbiturate, and 1,3-diethyl-2-thiobarbiturate with diarylcarbenium ions and Michael acceptors have been determined in dimethyl sulfoxide solution at 20 °C. The reactivity parameters N and s of the barbiturate anions were derived from the linear plots of log k versus the electrophilicity parameters E of these reference electrophiles, according to the linear-free-energy relationship log k (20 °C) = s (E + N). Several reactions of these nucleophiles with benzylidenemalononitriles and quinone methides proceeded with reversible formation of the new C-C-bond followed by rate-determining proton shift. No evidence for initial attack of the electrophiles at the enolate oxygens of these nucleophiles was found by the kinetic measurements, in line with quantum chemical DFT calculations, which showed that in all cases C-attack is kinetically and thermodynamically preferred over O-attack. The nucleophilic reactivities of barbiturate anions were compared with those of structurally related carbanions, e.g., Meldrum's acid and dimedone anions.

As a rule, acetylides and sulfonyl azides do not undergo electrophilic azide transfer because 1,2,3-triazoles are usually formed. We show now that treatment of tritylethyne with butyllithium followed by exposure to 2,4,6-triisopropylbenzenesulfonyl azide leads to products that are easily explained through the generation of short-lived tritylethynyl azide and its secondary product cyanotritylcarbene. Furthermore, it is demonstrated that tritylcarbenes generally do not produce triphenylethenes exclusively, as was stated in the literature. Instead, these carbenes always yielded also (diphenylmethylidene)cycloheptatrienes (heptafulvenes) as side products. This result is supported by static DFT, coupled cluster, and ab initio molecular dynamics calculations. From these investigations, the fused bicyclobutane intermediate was found to be essential for heptafulvene formation. Although the bicyclobutane is also capable of rearranging to the triphenylethene product, only the heptafulvene pathway is reasonable from the energetics. The ethene is formed straight from cyanotritylcarbene.

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