Unexpected Migratory Insertion Reactions of M(alkyl)2 (M=Zn,Cd) and Diamidocarbenes

The electrophilic character of free diamidocarbenes (DACs) allows them to activate inert bonds in small molecules, such as NH₃ and P₄. Herein, we report that metal coordinated DACs also exhibit electrophilic reactivity, undergoing attack by Zn and Cd dialkyl precursors to afford the migratory insertion products [(6‐MesDAC‐R)MR] (M=Zn, Cd; R=Et, Me; Mes=mesityl). These species were formed via the spectroscopically characterised intermediates [(6‐MesDAC)MR₂], exhibiting barriers to migratory insertion which increase in the order MR₂ = ZnEt₂ < ZnMe₂ < CdMe₂. Compound [(6‐MesDAC‐Me)CdMe] showed limited stability, undergoing deposition of Cd metal, by an apparent β‐H elimination pathway. These results raise doubts about the suitability of diamidocarbenes as ligands in catalytic reactions involving metal species bearing nucleophilic ligands (M‐R, M‐H).     

Improved Nucleophilic Displacements in N-Methyl Pyrrolidinone as a Solvent

The nucleophilic displacement reactions of 2- and 4- halogenonaphthalic-1,8, anhydrides and the N-imides, of 4,7- dichloroquinolines, the alkylation of lithio alkynes, the methylation of ethyl or methyl diacetylacetate and a variety of related reactions are greatly facilitated in N-methylpyrrolidinone as aprotic solvent.     

Identification and Quantification of Triterpenoid Centelloids in Centella asiatica (L.) Urban by Densitometric TLC

JPC – Journal of Planar Chromatography – Modern TLC - A simple and rapid method for analysis of four major triterpenoids in Centella asiatica preparations is described. Thin-layer...     

Isolation and Characterisation of All Four Diastereomeric Intermediates from a Horner-Wittig Reaction

Abstract

The Horner-Wittig reaction between diphenyl(2-phenylpropyl)phosphine oxide and 1-naphtaldehyde affords an equal mixture of the cis and trans isomers even though the formation of the initial adduct is selective.