Diastereoselective metal-catalyzed [4 + 2 + 2] carbocyclization reactions utilizing a rhodium N-heterocyclic carbene (NHC) complex: the first example of a rhodium NHC-catalyzed [m+n+o] carbocyclization

Abstract

The air and moisture stable rhodium N-heterocyclic carbene (NHC) complex, RhCl(IMes)(COD)(IMes =N,N[prime or minute]-bis(2,4,6-trimethylphenyl)imidazole-2-ylidine; COD = 1,5-cyclooctadiene), facilitates a diastereoselective metal-catalyzed [4 + 2 + 2] carbocyclization of 1,6-enynes in the presence of silver triflate and 1,3-butadiene.

Chromium(0)–rhodium(I) metal exchange: Synthesis and X-ray structure of new Fischer (NHC)carbene complexes of rhodium(I)

“…We selected the rhodium NHC-carbene complex 2, recently reported by Evans [13], as the appropriate starting rhodium(I) complex (Scheme 1). Firstly, chromium (methoxy)carbene complexes 1a-f (X = OMe) were reacted with 1 equiv.…”

“…2986,1931,1611,1421,1265,895,737 3.60 (s, 3H), 6.39 (d, J = 3.3 Hz, 1H), 6.43 (dd, J = 3.5 y 1.9 Hz, 1H), 6.92 (d, J = 14.7 Hz, 1H), 7.02 (s, 4H), 7.09 (s, 2H), 7.40 (bs, 1H), 7.93 (d,J = 14.7 Hz,1H). 13 2921,1932,1621,1485,1266,907,733 …”

Transition metals in organic synthesis: Highlights for the year 2005

“…Rhodium catalyzed a diastereoselective [4 + 2 + 2]cycloaddition of 1,6-enynes with 1,3-butadiene to give fused bicyclic compounds (Eq. (241)) [1287]. Cobalt catalyzed a [6 + 2]cycloaddition of cycloheptatrienes with alkynes [1288].…”

New metal-catalyzed carbocyclization reactions for the construction of complex natural products

“…23 The ability to vary the olefin geometry results in The stereospecificity with respect to the olefin geometry is consistent with the intermolecular case. 11 Moreover, while the origin of diastereocontrol with respect to the diene is not completely certain, it is consistent with an identical orientation of the diene in each case. This can presumably be attributed to non-bonding interaction between one of the isopropyl groups on silicon, and the protons on the 1,3-butadiene derivative.…”

“…In light of the success with the naphthyl substituted 1,6-enyne 10a, we elected to examine other substituents in order to determine the generality of this transformation. 6,11,12 Surprisingly, the extension of this methodology to other C-2 substituted 1,6-enynes, particularly alkyl derivatives, afforded only trace amounts of the product thus indicating that the original catalyst was highly substrate dependent. For example, treatment of the enyne 10b (R = Me) with this catalyst in the presence of 1,3-butadiene, afforded only trace amounts of the carbocycle 11b/12b (<5%).…”