Chemspec News: Gelest adds to cross-coupling agents
Provide economical alternative to tin and boron derivatives
US-based Gelest is showing its latest organosilicon, metal-organic and silicone-based innovations at Chemspec Europe in Berlin.
Gelest, a manufacturer of gram to multiple-ton quantities of silane, metal organic and silicone materials, has broadened its silicon-based cross-coupling agents to include aryl-, vinyl- and ethynyl silanes, which it says provide a non-toxic, easily handled, and economical alternative to commonly employed tin and boron cross-coupling derivatives.
The firm says these agents provide excellent flexibility for the formation of the carbon-carbon bond, whose strength and stability, coupled with carbon’s concatenation capability, enable the formation of a nearly limitless number of molecules for use in pharmaceuticals and a wide range of specialist chemical applications.
Gelest says its ability to form carbon-carbon bonds through the cross-coupling of an organic halide or pseudohalide with an organometallic reagent is drawing the attention of synthetic organic chemists as well as catalyst and specialist ligand providers. These reactions represent excellent elasticity for the formation of the carbon-carbon bond along with good functional group tolerance. One of these cross-coupling reactions, the Hiyama reaction, employs an organosilane as the organometallic partner in the cross-coupling reaction.
Many organic functional groups, ranging from carboxylic acids to aryl fluorides, may be reduced with a variety of organosilanes. The most popular is the easy-to-handle triethylsilane. However, the cost of using this organosilane can be expensive and it does not provide the most hydride for the weight.
Gelest can provide cost-effective reductions using the easy-to-handle, inexpensive and environmentally friendly polymethylhydrosiloxane (PMHS)-type materials as the reducing agent. PMHS siloxanes, in addition to costing much less than triethylsilane, carry considerably more hydride (1.35% on a molar basis) than triethylsilane (0.86% on a molar basis). PMHS reductions may be performed on olefins, aromatic and aliphatic halides, carboxylic acid and esters, aldehydes and ketones, imines, and reductive deallylation reactions. In addition, some highly useful asymmetric reductions may be performed on prochiral ketones, enones, α,β-unsaturated esters and lactones, and imines.
