Rhodium(I)‐Catalyzed Ring‐Closing Reaction of Allene–Alkene–Alkynes: One‐Step Construction of Tricyclo[6.4.0.0^2,6] and Bicyclo[6.3.0] Skeletons from Linear Carbon Chains

Abstract

Treatment of dodecatrienyne derivatives with [RhCl(CO) ] in refluxing toluene effected the cycloisomerization to produce tricyclo[6.4.0.0 ]dodecadienes. The one-carbon shortened undecatrienyne derivatives, however, afforded bicyclo[6.3.0]undecatriene derivatives instead of tricyclic compounds, the latter of which are well known as a basic skeleton of naturally occurring octanoids. On the basis of two experiments with deuterated substrates, a plausible reaction mechanism for the construction of these products was proposed.

Rh(i)-catalyzed dimerization of ene-vinylidenecyclopropanes for the construction of spiro[4,5]decanes and mechanistic studies

“…Instead of insertion into the neighboring cyclopropane, the rhodium( iii ) prefers to insert into the C–C bond of the distal cyclopropane to generate another rhodium( v ) intermediate Int6 via TS4 with a small energy barrier (1.3 kcal mol −1 ), probably due to the flexibility of the geometry of the medium-sized ring. 15 An alternative intermediate Int6′ was also investigated; however, its energy is much higher than that of Int6 by 34.8 kcal mol −1 . Subsequently, the rhodium( v ) intermediate Int6 undergoes a reductive elimination step to produce intermediate Int7 via transition state TS5; another possible intermediate Int7′ is also investigated.…”

Computational Study on Mechanisms and Origins of Selectivities in Rh(I)-Catalyzed Cycloisomerizations of 1,6-Allenynes with Tethered Unsaturated Carbon–Carbon Bonds

“…Experimental observation of the 6,8-bicyclic product in the cycloisomerization reaction of alkene-tethered 1,6-allenyne indicates that the carbon chain length of allenyne is significant to the product selectivity. 37 To clarify how carbon chain length influences the selectivity, cycloisomerization mechanisms of 1,5-and 1,7-allenyne were explored. The calculated results suggest that carbon chain length has no impact on the product selectivity in the reaction of alkyne-tethered 1,6-allenyne (Figure S16) because the selectivity-determining 1,2-migration is basically sensitive to the steric effect of the alkyne substituent (vide supra).…”

“…43,44 It was proposed that in the reaction of alkene-tethered 1,6-allenyne, the five-membered rhodacycle successively undergoes alkene insertion, β-hydride elimination, alkene reinsertion, and reductive elimination to yield the 6,5,5tricyclic product prod1. 37 However, in the reaction of alkynetethered 1,6-allenyne, II first undergoes σ-bond metathesis to form a four-membered rhodacycle VI, and then goes through alkyne insertion and reductive elimination to form product prod2. 38 While the above proposals may explain the generation of 6,5,5-tricyclic compounds from alkene-and alkyne-tethered 1,6allenynes, origins of the mechanistic differences between the two cycloisomerization reactions are less well understood.…”

“…Both cycloisomerizations include a C–H activation process. Recently, rhodium­(I)-catalyzed cycloisomerizations of 1,6-allenynes involving insertion of tethered unsaturated carbon–carbon bonds were reported by Mukai and co-workers (Scheme c,d). , Despite the different tethered groups (alkene or alkyne) within 1,6-allenynes, the two novel cycloisomerization reactions can both produce 6,5,5-tricyclic compounds. Moreover, diverse polycyclic skeletons (Figure ) could be produced through modifying the substrate or changing the ligand .…”

Engaging Yne‐Allenes in Cycloaddition Reactions: Recent Developments

“…Upon exposure to a catalytic amount of [RhCl(CO) 2 ] 2 in toluene at reflux, the same research group have achieved an attractive and convergent tricyclization of linear yne–allene–ene derivatives 81 , affording the functionalized tricyclo[6.4.0.0 2,6 ]dodecadienes 82 in 53%—96% yields with the complete diastereoselectivity (Scheme 25a). [ 82 ] The transformation exhibits good functional group tolerance and scalability, as demonstrated by various aryl, alkyl, phenylsulfonyl and phosphonate functionalities on the allenyl moiety. Of special interest is that use of one‐carbon shortened yne–allene–enes 83 enabled a different cycloisomerization direction, furnishing a series of the bicyclo[6.3.0]undecatriene compounds 84 via a bicyclization process in good yields (Scheme 25b).…”