1.1.1- Trihalides 1.1- dihalides, synthesis

The halides (especially the chloride) are the most commonly employed synthons in the chemistry of gallium. This is undoubtedly due to their ease of synthesis and high reactivity. While the trihalides have been traditionally the most extensively studied, the mono- and dihalides have come under recent scrutiny. 

Phospholenes generally have an envelope-shaped conformation (6.884). The most versatile method for the synthesis of phospholenes is the McCormack cycloaddition reaction using a diene and a phosphonous dihalide or a phosphorus trihalide [63,64]. 

A modified stepwise hydroboration avoiding the use of lithium aluminum hydride has also been developed (Schane 23.30). It was discovered that trialkylsilane reacts rapidly with boron trihalide to form unsolvated dihaloborane. Subsequent reaction with alkenes in the presence of sufficient boron trihalide occurs rapidly at -78°C to afford alkylboron dihalides without detectable contamination by dialkylboron halides. If additional equivalents of both trialkylsilane and alkene are added, dialkylboron halides are obtained. The methodology has been successfully applied to the synthesis of l,l,I-tris(dichloroboryl)alkanes, important precursors for dicarbapentaboranes. ... 

Ill Synthesis of monocyclic derivatives with diorganotin dihalides and organotin trihalides RnSnX -n and ... 

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