Allylation of Aldehydes Promoted by the Cerium(III) Chloride Heptahydrate/Sodium Iodide System: the Dependence of Regio‐ and Stereocontrol on the Reaction Conditions

Abstract

Abstract:The cerium(III) chloride heptahydrate/sodium iodide complex (CeCl 3 · 7 H 2 O/NaI) acts as a useful promoter in the carbon-carbon bond forming reaction by addition of allyltributylstannanes to aldehydes. The reaction of 2-butenyltributylstannane shows that the regio-and the stereochemical outcomes depend on the reaction conditions. When the promoter is adsorbed on a solid support (aluminum oxide), a highly prevalent formation of the g-adduct is observed in solvent-free conditions. Conversely, when the reaction is carried out in acetonitrile as the solvent, the a-adduct largely prevails. In the last case, a complete stereocontrol is observed, the less stable (Z)-isomer being obtained in high geometrical purity.

Applications of CeCl3 as an Environmental Friendly Promoter in Organic Chemistry

“…324 Recently, Quintard and co-workers 325 marvelously described how the analysis of the diastereomeric distribution on both the branched γ-adducts (ratio syn/anti) and the linear R-adducts (ratio Z/E) can be used to achieve a primary discrimination between a transmetalation and a simple Lewis acid assistance in the crotylstannane series (Scheme 62). In agreement with that, we have observed 322 with aromatic aldehydes and anti preference with both cyclic and linear aliphatic aldehydes. The methodology is very interesting because the reaction with γ-substituted allylstannanes generally proceeds with γ-regioselectivity 326 and only a few protocols for the regioselective synthesis of R-adducts have been reported.…”

“…The CeCl 3 • 7H 2 O-NaI promoted reaction shows that the regio-and the stereochemical outcomes depend on the reaction conditions. 322 The reaction can proceed either by simple Lewis acid assistance of the metal salt on the aldehyde 323 or through a preliminary transmetalation process between allylstannane and the cerium salt. 324 Recently, Quintard and co-workers 325 marvelously described how the analysis of the diastereomeric distribution on both the branched γ-adducts (ratio syn/anti) and the linear R-adducts (ratio Z/E) can be used to achieve a primary discrimination between a transmetalation and a simple Lewis acid assistance in the crotylstannane series (Scheme 62).…”

“…For this purpose, crotyltri- n -butylstannane has extensively been employed, and its condensation with aldehydes is an intriguing subject with respect to its regioselectivity (linear α-adducts/branched γ-adducts) and its stereoselectivity ( E / Z ratio in α-adducts or its syn / anti ratio in γ-adducts). The CeCl 3 ·7H 2 O−NaI promoted reaction shows that the regio- and the stereochemical outcomes depend on the reaction conditions . The reaction can proceed either by simple Lewis acid assistance of the metal salt on the aldehyde or through a preliminary transmetalation process between allylstannane and the cerium salt .…”

A SeCSe−Pd(II) Pincer Complex as a Highly Efficient Catalyst for Allylation of Aldehydes with Allyltributyltin

“…Such transition-metal-based catalysts invariably function as a Lewis acid in promoting the allylation reactions. A lanthanide, cerium(III) chloride (CeCl 3 •7H 2 O) in combination with NaI, has recently been introduced as a new, stoichiometric promoter for the allylation of various aldehydes with allyltributyltin . Yamamoto and co-workers first reported the Pt- and Pd-catalyzed allylation of aldehydes and imines with allyltributyltin (Scheme , eq 2) .…”

Efficient Transformation of Azides to Primary Amines Using the Mild and Easily Accessible CeCl3·7H2O/NaI System

“…The first step involves the addition of a triiodide ion, obtained by the known reaction of iodine with iodide ion, to an azide 1 . The addition is promoted by the ability of rare earth derivatives to coordinate multiple bond . On the basis of this mechanism, the iodide ion is widely consumed during the process, thus justifying the usage of an excess of NaI, and furthermore, to support our proposed mechanism, the reaction has been carried out in the presence of 2,6-di- tert -butyl-4-methylphenol as a radical inhibitor .…”