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.
Marrone
Alessandro
A
Dipartimento di Scienze del Farmaco, Università degli Studi G. d'Annunzio di Chieti-Pescara, Via dei Vestini, 66100 Chieti, Italy.
Renzetti
Andrea
A
De Maria
Paolo
P
Gérard
Stéphane
S
Sapi
Janos
J
Fontana
Antonella
A
Re
Nazzareno
N
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