Ring-expansion carbonylation

Abstract Development in the field of transition metal-catalyzed carbonylation of epoxides is reviewed. The reaction is an efficient method to synthesize a wide range of / -hydroxy carbonyl compounds such as small synthetic synthons and polymeric materials. The reaction modes featured in this chapter are ring-expansion carbonylation, alternating copolymerization, formylation, alkoxycarbonylation, and aminocarbonylation. 

The ring-expansion carbonylation of epoxides is the most widely studied field in the epoxide carbonylation chemistry since the product lactones are highly attractive targets particularly, /1-lactones are useful compounds due to their versatility in organic synthesis [ 14,15] as well as their utilization as monomers to produce poly(3-hydroxyalkanoate)s, naturally occurring biodegradable polyesters [16-19]. 

The first successful example of a catalytic ring-expansion carbonylation was reported by Aumann et al. in 1970s [20,21], Here, isoprene oxide was allowed to react with CO in the presence of [Rh(cod)Cl]2 to give an fi,y-unsaturated lactone (Scheme 2). Soon after their report, the carbonylation of styrene oxide to yield the corresponding /1-lactone was demonstrated by using RhCl(CO)(PPh3)2 [22], The scope of this method is, however, quite... 

Poly(3-hydroxyalkanoate)s have potential for application to engineering plastics endowed with biodegradable nature. One of the synthetic approaches to the polyesters is the ring-opening polymerization of -substituted /3-lactones which can be effectively produced by ring-expansion carbonylation of epox-... 

Ring expansion-carbonylation.1 The ring expansion of aziridines to /3-lactams by a Rh(l) catalyst (15,82-83) has been extended to expansion of pyrrolidines to piperidones by cobalt carbonyl-catalyzed carbonylation (equation 1). 

Altihough many of the early examples of the carbonylation of heterocycles included reactions of tetrahydrofurans, oxetanes, and azetidines, the majority of recent work has focused on the reactions of epoxides and aziridines. At this point, the ring-expansive reactions of epoxides are more general than the reactions of aziridines and occur imder milder conditions. Prior to 1994, ring-expansive carbonylation of epoxides was restricted to a few substrates. The patent by Droit and Kragtwijk s in 1994 inspired further work on these t)rpes of carbonylations, and tiiis work led to dramatic improvements in reaction scope. 

Disubstituted epoxides undergoing ring-expansion carbonylation by catalysts 4 and 5 of Scheme 17.24. 

Palladium-catalyzed ring expansion-carbonylation of azirines. 

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