Condensation of beta-diester titanium enolates with carbonyl substrates: a combined DFT and experimental investigation.
The condensation of dialkyl beta-diesters with various aldehydes promoted by TiCl4 has been studied by DFT approaches and experimental methods, including NMR, IR and UV/Vis spectroscopy. Various possible reaction pathways have been investigated and their energy profiles evaluated to find out a plausible mechanism of the reaction. Theoretical results and experimental evidence point to a three-step mechanism: 1) Ti-induced formation of the enolate ion; 2) aldol reaction between the enolate ion and the aldehyde, both coordinated to titanium; and 3) intramolecular elimination that leads to a titanyl complex. The presented mechanistic hypothesis allows one to better understand the pivotal role of titanium(IV) in the reaction.
Dipartimento di Scienze del Farmaco, Università degli Studi G. d'Annunzio di Chieti-Pescara, Via dei Vestini, 66100 Chieti, Italy.
Alessandro
A
Marrone
Andrea
A
Renzetti
Paolo
P
De Maria
Stéphane
S
Gérard
Janos
J
Sapi
Antonella
A
Fontana
Nazzareno
N
Re
D000447:Aldehydes / Q000737:chemistry*; D000465:Algorithms; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008314:Malonates / Q000737:chemistry; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*
D000447:Aldehydes; D008314:Malonates; C498810:diethyl malonate; C025096:titanium tetrachloride; D014025:Titanium