Magnesium compounds alkynylation

A large variety of cuprates are known nowadays. They include heteroleptic derivatives R(Y)CuM (Y = alkynyl, halide, amido, alkoxide, thiolato, phosphide M = Li or Mg), and have found widespread application in organic chemistry. Their syntheses and applications are discussed in the other chapters of this book. In addition, compounds in which the copper to lithium (or magnesium) ratio differs from 1 1 are also known examples are R3CuLi2 and the so-called higher order cyanocuprates introduced by Lipshutz et al. [99]. 

Alkenyl, alkynyl, and aryl halides, like alkyl halides, can be converted to the corresponding magnesium and lithium compounds. However, the reaction conditions, such as choice of solvent, can be critical. Bromoethene, for instance, can be converted to ethenylmagnesium bromide in good yield if the solvent is oxacyclopentane [tetrahydrofuran, (CH2)40] ... 

In the majority of cases, organolithium compounds and Grignard reagents contain polarized but covalent carbon—metal bonds. Lithioalkanes, -alkenes, and -aromatics, on the one hand, and alkyl, alkenyl, and aryl magnesium halides, on the other hand, are therefore formulated with a hyphen between the metal and the neighboring C atom. Only lithiated alkynes and alkynyl Grignard reagents are considered to be ionic—that is, species with carbon, metal bonds similar to those in LiCN or Mg(CN)2. 

Triorganoaluminums with unsaturated C—C bonds adjacent to AI can be prepared from the respective organolithium, -sodium or -magnesium halide reagents. However, the solvate-free compounds (R = alkenyl, alkynyl) are unstable and, therefore, should be isolated as ether adducts ... 

T -Complexes contain a metal-carbon single bond (Figure 1.1). The organic group may be alkyl, vinyl, alkynyl, aryl or acyl. With the exception of the acyl complexes, there are analogous compounds of more familiar metals, such as magnesium and zinc. It is also possible to have complexes with metal-carbon double and triple bonds these are known as carbenes and carbines. Cumulenes are also known, such as in vinylidene complexes. 

Cyclopropanone Hemiacetals and Their Use. Mild alcoholysis of the silyloxycyclopropane gives a cyclopropanone hemi-acetal. This compound serves as a stable equivalent of unstable cyclopropanones. Treatment with two equivalents of alkynyl-magnesium bromide gives a 1-ethynyl-l-hydroxycyclopropane (eq 14). ... 

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