The Contribution Made by Triphenylphosphane in the Putative Catalysis by Ruthenium Species in Conjugate Additions of β-Dicarbonyl Compounds

Abstract

Triphenylphosphane catalyzes conjugate additions of β-dicarbonyl compounds to π-acceptor olefins and dialkyl azodicarboxylates. Formation of quaternary centers at the nucleophiles has been achieved. The catalytic action of tris(triphen-

Conjugate Additions to Vinyl-Substituted Aromatic N-Heterocycles

“…In a ruthenium-catalyzed reaction, the conjugate addition product 10 is formed, however, it reverts to starting materials during chromatography or distillation. 11 Nevertheless, the unstable addition product may be trapped by hydrazine to give the functionalized pyrazole 11 in fair yield (Scheme 5).…”

Nitrogen-nitrogen bond cleavage catalyzed by ruthenium complexes

“…However, when the same reaction was catalyzed by tetrakis(triphenylphosphane)ruthenium(II) hydride, 9 unexpected compounds were isolated. 10 The formation of 4 and 5 must involve the cleavage of the N-N bond. Initially, phosphane was proposed to be responsible for the N-N activation.…”

“…Curiously enough, RuH 2 (PPh 3 ) 4 was not a good catalyst for this transformation, and starting material was recovered after 24 hours (Entry 3). This result was initially quite surprising for us, taking into account our previously mentioned results (Scheme 1) 10 . However quite recent results in the literature indicate that hydrogenolysis of 6a can be only achieved using RuH 2 (PPh 3 ) 4 under high hydrogen pressures.…”

“…17 These compounds can be easily achieved by Michael addition reactions. 10,18 The cleavage of nitrogen-nitrogen bonds of the alkylhydrazino groups would be a good method to introduce amino functions in the intercarbonylic position (electrophilic amination). 19 If starting materials are β-ketoesters, this cleavage process would allow to achieve α-aminoacid derivatives.…”

Phosphine-Initiated General Base Catalysis: Facile Access to Benzannulated 1,3-Diheteroatom Five-Membered Rings via Double-Michael Reactions of Allenes

“…The cyclic enolate 14 can further facilitate the double-Michael reaction cycle by deprotonating the pronucleophile 1 (or mono-Michael product; e.g., 5a in Scheme 1) to produce the product 4 , supporting the notion of general base catalysis. 23 The observation of no cyclized product derived from the allenoate 2a in Eq 3 also suggests that the second Michael addition is facile and that the intermediate 11 does not revert back to the allenoate 2 and the nucleophile 7 .…”