Alkynes laboratory application

Hydroboration is the term given to the addition of a boron-hydrogen bond to either the carbon-carbon double bond of an alkene (Equation B 1.1) or the carbon-carbon triple bond of an alkyne (Equation B1.2). The first examples of hydroboration were reported in 1956 from the laboratories of H.C. Brown and since then the reaction has found many important applications in organic chemistry. Indeed, in 1979 Brown was awarded the Nobel chemistry prize for his contributions to hydroboration and related areas of reactivity. 

The reaction of an alkene (or alkyne), CO, and H2O to directly produce a carboxylic acid is called Reppe carbony-lation chemistry or, more recently, hydrocarboxylation see Reppe Reaction). An excellent review of palladium-catalyzed Reppe carbonylation systems has been published recently by Kiss, and coverage of this important material will not be repeated here. This catalytic reaction has been known for quite some time, although the stoichiometric Ni(CO)4-based carbonylation of acetylene was the first commercial carbonylation process implemented (equation 13). The extreme toxicity of Ni(CO)4, however, has limited practical applications see Nickel Organometallic Chemistr. Co, Rh, and Pd catalysts have certainly replaced Ni(CO)4 in smaller-scale laboratory reactions, though for historical reasons a number of the fundamental mechanisms discussed in this section are based on Ni(CO)4. 

Like many carbonylation processes, the hydrocarboxylation and hydroesterification reactions were first reported by Reppe. These first reactions involved the hydrocarboxylation of alkynes. These reactions were conducted with nickel carbonyl as catalyst and occurred with very low turnover numbers. Hydrocarboxylation and hydroesterification have now been studied extensively in both academic and industrial laboratories. As a result of these investigations, commercialization of this chemistry as part of new industrial processes has occurred, and the mechanism of these processes is now generally accepted. This section of Chapter 17 presents the scope and industrial applications of hydrocarboxylation and hydroesterification, the types of catalysts that have been used for these processes, and the elementary steps that constitute the catalytic cycle for olefin and alkyne hydroesterification. 

---