Rearrangements involving allenes

Thermal Rearrangements of 1-Ethynyl-2-methylcyclopropane: A Computational Study

“…In their experiments, methylenecyclopentenes 5 and 6 were also formed. They also observed that the ratio of methylenecyclopentenes is [ 6 ]/[ 5 ] = 1.3, which is consistent with Huntsman et al’s and Andrews and Baldwin’s predictions (Scheme ) . Moreover, it was proposed that 2 undergoes a 1,3-hydrogen shift to form 1,3,5-hexatriene ( 10 ), which was not observed, but its electrocyclization product, 1,3-cyclohexadiene ( 11 ), was isolated.…”

“…The 1-ethynyl-2-methylcyclopropane ( 1 ) molecule is an important species; its thermal aromatization reaction is closely related to several interesting systems, such as the Huntsman–Baldwin–Roth mechanism − , and Berson trimethylenemethanes (Berson-TMMs). ,− In this study, a comprehensive theoretical investigation of the thermal rearrangements of 1-ethynyl-2-methylcyclopropane is carried out employing density functional theory (DFT) and high-level ab initio methods. The potential energy surface (PES) for the relevant system (Scheme ) is explored to provide a theoretical account of experiments by Hopf, − Ellis and Frey, Huntsman et al, and Berson .…”

Unprecedented Allenylidene Transfer from Chromium to Tungsten

“…Such a mechanism is also not in accord with the experimental results (see above). Furthermore, examples of free allenylidenes are very scarce 6 …”

C−N and C−C Coupling Reactions: Preparation of New N-Heterocyclic Ruthenium Derivatives

“…Since the formation of 7 involves the deprotonation of 6 (the isomeric mixture of 6a and 6b ) and it is well-known that the deprotonation of tertiary azoniabutadienyl complexes proceeds by extraction of the proton of the CHCPh 2 group, it is reasonable to assume that one of the key steps of the process is the formation of an aminoallenyl intermediate. It is also well-known that bases can catalyze the isomerization of propargylic into allenic moieties; therefore, another key step of the process should be the isomerization of the aminopropargyl group into aminoallenyl. In this context, it should be noted that, under the conditions of the reaction shown in eq 5, complex 4 is stable.…”