Catalytic ring expansion

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... 

More recently, the same principle was applied by the same authors to cyclic alkanes for catalytic ring expansion, contraction and metathesis-polymerization (Scheme 13.24) [44]. By using the tandem dehydrogenation-olefin metathesis system shown in Scheme 13.23, it was possible to achieve a metathesis-cyclooligomerization of COA and cyclodecane (CDA). This afforded cycloalkanes with different carbon numbers, predominantly multiples of the substrate carbon number the major products were dimers, with successively smaller proportions of higher cyclo-oligomers and polymers. 

The opened epoxide shown in Fig. 15 is also an intermediate in the catalytic ring expansion of epoxides to p-lactones (see Sect. 8.4). In this context, Drent and coworkers patented a catalytic system of dicobaltoctacarbonyl Co2(CO)g and... 

Catalytic ring expansion ofthiiranes, aziridines, and oxiranes 13SL787. Organocatalysis in synthesis and reactions of epoxides and aziridines 13RCA11385. 

The first catalytic ring-expansion reaction of vinyl oxetane (147) in the presence of chiral Bronsted sulfonamide (149) provided 3,6-dihydro-21f-pyran (148) with 90% ee (Scheme 52). ... 

When aziridine 194 (Scheme 3.71) was treated with a catalytic amount of NaOEt in ethanol it underwent an intramolecular ring-expansion to pyrrolidinone 195 in 88% yield [130]. The ring-opening took place via an internal SN2 reaction, which was confirmed by an X-ray analysis of the product 195. It is interesting to note that under similar reaction conditions 196 (Scheme 3.72) afforded P-lactam product 197 [130]. 

Treatment of compounds 44 with a catalytic amount of sodium ethoxide in ethanol led to a smooth intramolecular reaction, which resulted in the formation of y-lactams 45 in good yields [45] (Scheme 35). The stereochemical course of this ring expansion was unambiguously established by an X-ray analysis of product 45 [45]. Clearly an intramolecular Sn2 reaction has taken place. 

The Zr-catalyzed ethylalumination of alkynes under certain conditions1,9 (Scheme 4) and ethylmagnesation of alkenes10 11 (Scheme 5) represent some of the earliest examples of the catalytic carbozirconation proceeding via zirconacycles. In Scheme 5, the carbometallative ring expansion of (ethylene)zirconocene to produce a... 

The Rh-catalyzed ring-expansion reaction of thiazolidine 246 in the presence of a catalytic amount of KI (2 mol%) at 180°C and 65 atm of CO gave thiazolidinone 251 in 56-88% yields. Formation of thiomorpholinone 252 was not observed at all. Thus, a proposed mechanism of this reaction involves the elimination of a ketene molecule from a key intermediate 248 to form rhodathiazolidine complex 249, which undergoes migratory CO insertion, followed by reductive elimination to yield thiazolidinone 251 (Scheme 36). ... 

The deoxygenative ring expansion of nitrobenzene with tri-n-butylphosphine in butanol (77BCJ2013), or with phosphorus trichloride and di-n-butylamine in hexane, followed by catalytic reduction and hydrolysis of the resulting 2-butoxy- or 2-butylamino-3//-azepines have been patented as methods for the production of caprolactam (78JAP(K)78132586, 77GEP2647936 respectively). 

The reaction of methylenecyclopropanes with transition metal complexes is well known to promote a catalytic a-ir cycloaddition reaction with unsaturated compounds, in which a trimethylenemethane complex might exist71-76. Recently, much interest has been focused on the interaction of strained silicon-carbon bonds with transition metal complexes. In particular, the reaction of siliranes with acetylene in the presence of transition metal catalysts was extensively investigated by Seyferth s and Ishikawa s groups77-79. In the course of our studies on alkylidenesilirane, we found that palladium catalyzed reaction of Z-79 and E-79 with unsaturated compounds displayed ring expansion reaction modes that depend on the (Z) and (E) regiochemistry of 79 as well as the... 

Theoretical studies have also been reported on the catalytic activity of the rhodium (I) in the carbonylative ring expansion of aziridines to (3-lactams [151]. 

Rh-complexes in carbonylative ring expansion reactions of a variety of aziridines with carbon monoxide, which resulted in the formation of (3-lactams in good yields. It was reported that the catalytic system could be easily recovered by simple filtration and recycled without significant loss of activity. 

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