Esterification and etherification of steroid and terpene under Mitsunobu conditions

The synthesis and study of steroids and terpenes continues to be a topic of widespread interest, the esterification and etherification under Mitsunobu conditions of primary alcohol such as geraniol prepared in 95% yield, and when a chiral secondary alcohol such as cholesterol or menthol is used, sufficient configurational inversion of alcohol with 65% yield, but the reaction of tertiary alcohols the α-terpeniol for example are rare

Regio- and stereoselective synthesis of novel isoxazolidine heterocycles by 1,3-dipolar cycloaddition between C-phenyl-N-methylnitrone and substituted alkenes. Experimental and DFT investigation of selectivity and mechanism

International audienceA series of isoxazolidine heterocycles was synthesized through the 1,3-dipolar cycloaddition (13DC) reaction of C-phenyl-N-methylnitrone with different substituted alkenes. The structures and stereochemistry of the cycloadducts were determined by spectroscopic methods. These 13DC reactions are characterized by complete regioselectivity and high stereoselectivity. The molecular mechanism, reactivity and selectivity of these 13DC reactions have been investigated by means of transition state theory and reactivity indices derived from conceptual DFT using DFT methods at the B3LYP/6-31G(d,p) level of theory. The obtained results indicate that these cycloaddition reactions take place through a one-step synchronous mechanism with a non-polar mechanism and high activation energies. The theoretical results are in agreement with the experimental findings

A theoretical study of the regio- and stereoselectivities of non-polar 1,3-dipolar cycloaddition reaction between <i>C</i>-diethoxyphosphoryl-<i>N</i>-methylnitrone and <i>N</i>-(2-fluorophenyl)acrylamide

<p>The 1,3-dipolar cycloadditions (13DC) of <i>C</i>-diethoxyphosphoryl-<i>N</i>-methylnitrone and N-(2-fluorophenyl) acrylamide have been studied using density functional theory (DFT) calculations at B3LYP/6-31G(d) level of theory. Our calculations show that this 13DC reaction takes place with complete <i>ortho</i> regioselectivity with <i>endo</i> stereoselectivity, which favours kinetically the formation of the <i>ortho</i>–<i>endo</i> cycloadduct, in agreement with the experimental observations. The inclusion of solvent effects does not modify the gas-phase selectivities but slightly decreases the reactivity of the reagents. Analysis of the bond order and charge transfer at the transition states indicates that this 13DC reaction takes place <i>via</i> a one-step asynchronous mechanism. Analysis of the DFT global reactivity indices and the Parr functions of the reagents allow us to provide an explanation of the regioselectivity of this 13DC reaction.</p> <p></p