Stereoselectivity in Intramolecular Diene Cyclozirconation: A Combined Experimental and Theoretical Approach
摘要:
Intramolecular diene cyclozirconation (1 --> 2 + 3 --> 4) can be highly diastereoselective (97:3 trans/cis for 4). It is suggested that the cis and trans diastereomers of the zirconacycle are equilibrating under the conditions of the reaction, and that the observed diastereomeric preference of 4 reflects the relative stability of the two diastereomeric zirconacycles. Results for the intramolecular cyclozirconation of two other dienes, 8 and 14, as well as for the ''heterodiene'' N,N-diallylaniline are also reported. Computational results at the molecular mechanics, semiempirical molecular orbital ZINDO and nonlocal density functional theory levels are used to explain the observed stereochemistry in terms of thermodynamic and kinetic control.
An improved procedure for the synthesis of allylic spiro-γ-lactones
作者:Jagattaran Das、Prabir K. Choudhury、Srinivasan Chandrasekaran
DOI:10.1016/0040-4020(95)00067-i
日期:1995.3
Allylic spiro-γ-lactones of the type 4 have been synthesised in two steps starting from the carbonyl precursors using heterogeneous permanganate oxidation as the key step.
Enantioselective Cu-Catalyzed 1,4-Addition of Grignard Reagents to Cyclohexenone Using Taddol-Derived Phosphine-Phosphite Ligands and 2-Methyl-THF as a Solvent