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Regioselective addition of Ti enolates to conjugated enones: New insights into the mechanism based on experimental and DFT investigation
- Source :
- Tetrahedron. 74:2819-2824
- Publication Year :
- 2018
- Publisher :
- Elsevier BV, 2018.
-
Abstract
- The regioselective addition mechanism of the Ti(IV) enolates derived from α-diazo-β-keto carbonyl compounds and α-diazo-β-keto phosphonates to conjugated enones has been studied on the basis of a hypothetical bridging chloride-controlled theory, by density functional theory (DFT), and experimentally. The DFT results indicate that, for the Ti(IV) enolate 3 derived from α-diazo-β-keto carbonyl compounds, the free energy of the bridging chloride-controlled 1,2-addition transition state is 2.4 kcal/mol higher than that of 1,4-addition, and the calculated enthalpies of 1,2-addition is 4.36 kcal/mol more than that of 1,4-addition. For the Ti(IV) enolate 4 derived from α-diazo-β-keto phosphonates, in contrary, the free energy of the bridging chloride-controlled 1,2-addition transition state is 1.1 kcal/mol lower than that of 1,4-addition, and the calculated enthalpy of 1,2-addition is 3.46 kcal/mol less than that of 1,4-addition. Our findings demonstrate that the nucleophilic addition of these Ti(IV) enolates to conjugated enones was carried out not only kinetically but also irreversibly for the first time.
Details
- ISSN :
- 00404020
- Volume :
- 74
- Database :
- OpenAIRE
- Journal :
- Tetrahedron
- Accession number :
- edsair.doi...........60e4051fcd8c76043373e1bb417b6682