Reactions of bis(trimethylsilyl)bromomethyllithium and tris(trimethylsilyl)methyllithium. the synthesis of α-bromovinylsilanes

Modern synthetic methods for fluorine-substituted target molecules

Fluorine has come to be recognized as a key element in materials science: in heat-transfer agents, liquid crystals, dyes, surfactants, plastics, elastomers, membranes, and other materials. Furthermore, many fluorine-containing biologically active agents are finding applications as pharmaceuticals and agrochemicals. Progress in synthetic fluorine chemistry has been critical to the development of these fields and has led to the invention of many novel fluorinated molecules as future drugs and materials. As a result of the electronic effects of fluorine substituents, fluorinated substrates and reagents often exhibit unusual and unique chemical properties, which often make them incompatible with established synthetic methods. Thus, the problem of how to control the unusual properties of compounds with fluorine substituents deserves much attention, so as to promote the design of facile, efficient, and environmentally benign methods for the synthesis of valuable organofluorine targets.

Simple diastereoselectivity on addition of alpha-haloalkyl Grignard reagents to benzaldehyde

The addition of alpha-haloalkyl Grignard reagents to benzaldehyde occurs with simple diastereoselectivity substantially higher than that of the corresponding lithium reagents. Reaction in the presence of dimethyl-aluminum chloride suppresses subsequent Oppenauer oxidation of the resulting Mg-alkoxides by excess benzaldehyde.

Pericyclic Reactions of Free and Complexed Cyclopentyne

The selectivity between [2 + 2] and [2 + 4] cycloadditions of cyclopentyne with spiro[2.4]nona-2,4-diene depends on the mode of generating the cycloalkyne. Using diazomethylenecyclobutane and (bromocyclobutylidenemethyl)trimethylsilane as precursors affords cyclopentyne in an unencumbered form, whereas using dibromomethylenecyclobutane and 1,2-dibromocyclopentene yields a cyclopentyne-lithium bromide complex.