Rhodium(I) catalysed rearrangements of vinyl epoxides and oxetans

Abstract

RhI catalysed rearrangements of vinyl epoxides to ccp-unsaturated aldehydes and cleavage of oxetans to olefins and aldehydes are described and the reactions interpreted in terms of RhI acting as a weak Lewis acid. RECENTLY, we described some rearrangements of cycloolefinic epoxides in the presence of [Rh(CO),Cl],. Some

Development of a Hydrazine-Catalyzed Carbonyl-Olefin Metathesis Reaction

“…Grigg reported in 1972 that [Rh(CO) 2 Cl] 2 catalyzed this same cycloreversion under rather mild conditions (Scheme 4b). 11 It is most probable that the rhodium catalyst was acting simply as a Lewis acid, inducing stepwise cycloreversion via initial rupture of the bisbenzylic C-O bond. It can be imagined that this catalytic cycloreversion could be conducted in tandem with the photocycloaddition to produce bicycle 50, thereby realizing a one-step process, but this combination has not yet been reported.…”

Reactions of palladium(II) chloride with aziridine rings. Catalytic rearrangement of N-carbethoxy-8-azabicyclo[5.1.0]oct-3-ene to N-carbethoxynortropidine

“…Received August 1,1975 Abstract: The isomerizations of 3-methyl-3-cyclohexenone (1) to 3-methyl-2-cyclohexenone (2), and 1 -acetyl-2-cyclohexene (5) to 1 -acetyl-1 -cyclohexene (6) are efficiently catalyzed by trifluorethylamine (TFEA). In the case of 1 -2, the reaction proceeds via the intermediate formation of trifluoro-A-(3-methyl-2-cyclohexenylidene)ethylamine (3), the Schiff base of TFEA and 2.…”

“…Both reactions are diagnostic of the palladiumcarbon bond. In addition, 13 phos to give the stable complex 8, and 8 also carbonylates to give 6. The NMR spectrum of ester 6 is particularly informative with respect to several reaction stereochemistries.…”

“…It is also possible that a 1,2-Pd/H interchange occurs followed by a fast /3-chloride elimination to give 4. A fast /3-chloride elimination following the 1,2-Pd/H interchange would also account for lack of scrambling of -CO2CH3 between positions 2 and 3 in the 13/ CO/CH3O-reaction product (6).…”

Carbonyl–Olefin Metathesis

“…Oxetane fragmentation to carbonyl–olefin metathesis products has also been reported with catalytic amounts of Rh­(I) complexes functioning as Lewis acids (Scheme ). Specifically, Grigg and co-workers investigated the rearrangements of epoxides and oxetanes in the presence of [Rh­(CO) 2 Cl] 2 and discovered that oxetane 45 fragments to provide 46 , quantitatively, incorporating a newly formed aldehyde and trisubstituted olefin. Likewise, oxetane 50 results in furan 51 and benzaldehyde 49 upon treatment under identical reaction conditions, albeit shorter reaction times (Scheme ).…”