The kinetics and mechanism of the phosphorus-catalysed dimerisation of acrylonitrile

Organocatalytic Michael Cycloisomerization of Bis(enones): The Intramolecular Rauhut−Currier Reaction

“…As demonstrated by the Morita−Baylis−Hillman reaction, nucleophilic organic compounds also may serve as efficient catalysts for enone activation . Though realized in the context of aldehyde addition, the mechanistic motif embodied by the Morita−Baylis−Hillman reaction may encompass other electrophilic partners, including electron-deficient alkenes. − Indeed, the phosphine-catalyzed dimerization of electron-deficient alkenes reported by Rauhut and Currier predates the Morita−Baylis−Hillman reaction 5a. While the intramolecular Morita−Baylis−Hillman reaction is known, the intramolecular Rauhut−Currier reaction has not been described. , In this account, we report an intramolecular variant of the Rauhut−Currier reaction, i.e.…”

“…Though detailed mechanistic studies have not been undertaken, a plausible mechanism for the phosphine-catalyzed cycloisomerization of bis(enones) is proposed below . Conjugate addition of tributylphosphine I to the indicated bis(enone) provides enolate II .…”

The Vinylogous Intramolecular Morita−Baylis−Hillman Reaction: Synthesis of Functionalized Cyclopentenes and Cyclohexenes with Trialkylphosphines as Nucleophilic Catalysts

“…The Morita−Baylis−Hillman (MBH) reaction involves the α-hydroxyalkylation and α-aminoalkylation of Michael acceptors by electrophilic carbonyl compounds or imines in the presence of a nucleophilic catalyst such as a tertiary amine or phosphine. − Surprisingly, there have been relatively few applications of this technology to cyclization processes. − We are also unaware of examples of a potentially important variant, which we term the vinylogous intramolecular Morita−Baylis−Hillman reaction, in which an α,β-unsaturated carbonyl compound serves as a Michael acceptor in the electrophile capture step (see 1 → 2 or 3 → 4 ). It is known that acrylates and enones will dimerize under MBH reaction conditions, − and that enones can be α-alkylated in a Michael reaction with acrylates and acrylonitrile in the presence of DBU at 185 °C . Ring closing reactions are known that proceed via 1,4-addition of organometallic and heteronucleophilic reagents to enones or enoates such as 1 and 3 , with subsequent addition of the initial enolate to the second Michael acceptor. − Lithium amides and thiolates have been used to initiate such cyclizations; however, the nucleophiles remain covalently attached in the cyclization products. , In principle, a subsequent elimination step could be employed to access the targeted unsaturated ring systems 2 and 4 .…”

Polarity Inversion Catalysis by the 1,4-Addition of N-Heterocyclic Carbenes

“…Related phosphine-catalyzed dimerizations of electron-poor olefins have been examined sporadically in the years following this report, [8] often in the context of non-electrochemical routes to adiponitrile. Most recently, Han and coworkers reported the dimerization of vinylphosphonate 8 to give 9 in 48 % yield in the presence of a catalytic trialkyl phosphine (Scheme 3).…”