Intramolecular hydroesterification

In the reaction of aHyl alcohol with carbon monoxide using cobalt carbonyl, Co(CO)g as the catalyst, in the presence of a small amount of hydrogen and carbon monoxide under pressure, 9.8 MPa (1420 psi), at 100°C, intramolecular hydroesterification takes place, yielding y-butyrolactone [96-48-0] (16). 

Intramolecular condensation of co-hydroxycarboxylic acids is a standard method to prepare lactones. Acid catalysts or more elaborate mediators are usually required as well as continuous removal of water. Transition-metal-catalyzed cyclocarbonylation of unsaturated alcohols is a fascinating alternative, which proceeds under neutral conditions [26]. Intramolecular hydroesterification of... 

The intramolecular hydroesterification of olefins provides a route to lactones. Alihough this reaction has not been applied extensively in the synthesis of complex molecules, several examples demonstrating the scope and potential utility of this reaction have been reported, As shown in Equations 17.42-17.44 this reaction can be used to prepare optically active lactones,benzo-fused lactones, and lactams. The reaction in Equation 17.43 illustrates how the product can result from a combination of isomerization and carbonyla-tion, and the reaction in Equation 17.44 shows how the ring size can be controlled by the composition of the catalyst. 

In the presence of various functional groups in an appropriate distance from the alkenyl or alkynyl moieties, substituted alkenes or alkynes may undergo tandem reactions comprising hydroesterification as one of the individual steps. The bicylic cis-fused lactone core of plakortones, a novel class of activators of cardiac SR-Ca -pumping ATPase, was efficiently accessed by a palladium(II)-mediated cyclization-intramolecular hydroesterification reaction sequence. Cyclization of the starting enediols was carried out using either a small excess of Pd(II) [47] or a catalytic amount of Pd(II) and an excess of Cu(II) as the reoxidant [48],... 

The intramolecular version of hydroesterification was used for the synthesis of steroidal 17-spirolactones such as the aldosterone antagonist eplerenone starting from 17-hydroxy-17-vinyl or 17-hydroxy-17-ethynyl derivatives [46]. 

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