896155-83-2Relevant academic research and scientific papers
Intramolecular cyclization manifolds of 4-Alkylpyridines bearing ambiphilic side chains: Construction of spirodihydropyridines or benzylic cyclization via anhydrobase intermediates
Parameswarappa, Sharavathi G.,Pigge, F. Christopher
, p. 8038 - 8048 (2013/01/15)
4-Alkylpyridines possessing nucleophilic β- dicarbonyl side chains have been converted to spirodihydropyridines upon treatment with ethyl chloroformate and sub-stoichiometric amounts of Ti(OiPr)4. Alternatively, inclusion of mild base in the reaction medium was found to facilitate generation of anhydrobase intermediates. Subsequent aldol-like condensations with electrophilic side chain moieties followed by hydrolysis delivered benzylically cyclized pyridines in good yield. In situ hydrogenation of cyclized anhydrobase intermediates afforded 4-substituted piperidines.
Modulation of the reactivity, stability and substrate- and enantioselectivity of an epoxidation catalyst by noncovalent dynamic attachment of a receptor functionality - Aspects on the mechanism of the Jacobsen-Katsuki epoxidation applied to a supramolecular system
Jonsson, Stefan,Odille, Fabrice G. J.,Norrby, Per-Ola,Waernmark, Kenneth
, p. 1927 - 1948 (2008/02/03)
The synthesis of the components of the dynamic supramolecular hydrogen-bonded catalytic system 2 + 3 is described. The catalytic performance and substrate- and enantioselectivity of Mn(salen) catalyst 2 were investigated in the presence and absence of the Zn(porphyrin) receptor unit 3. The effects of pyridine and pyridine N-oxide donor ligands were also studied. Some aspects on the mechanism of the Jacobsen-Katsuki epoxidation, based on literature observations, are introduced as a means to analyse the behaviour of 2 and its modulation by the formation of macrocycle 1 with 3. A complete association model of the metal-free system 4 + 5 refutes the earlier assumption that macrocycle 1 is the predominant form of catalyst 2 under the standard epoxidation reaction conditions with 2 + 3. Evidence are provided that receptor-binding substrates and nonbinding substrates, respectively, are epoxidised by two different catalytic species, or two distinct distributions of species in competitive epoxidations using catalytic system 2 + 3. The two species are assigned to the endo and exo faces of the Mn(salen) catalyst in macrocycle 1, and to equivalently folded oligomeric structures with monomers 2 and 3 in adjacent positions. The Royal Society of Chemistry 2006.
