Silicon-Initiated Carbonylative Carbotricyclization and [2+2+2+1] Cycloaddition of Enediynes Catalyzed by Rhodium Complexes

Abstract

The reaction of dodec-11-ene-1,6-diynes or their heteroatom congeners with a hydrosilane catalyzed by Rh(acac)(CO)2 at ambient temperature and pressure of CO gives the corresponding fused 5-7-5 tricyclic products, 5-oxo-1,3a,4,5,7,9-hexahydro-3H-cyclopenta[e]azulenes or their heteroatom congeners, in excellent yields through a unique silicon-initiated cascade carbonylative carbotricyclization (CO-SiCaT) process. It has also been found that the 5-7-5 fused tricyclic products can be obtained from the same type of enediynes and CO through a novel intramolecular [2+2+2+1] cycloaddition process. The characteristics of these two tricyclization processes and the fundamental differences in their reaction mechanisms are discussed. This novel higher-order cycloaddition reaction has also been successfully applied to the tricyclization of undeca-5,10-diyn-1-als, affording the corresponding 5-7-5 fused-ring products bearing a seven-membered lactone moiety. Related [2+2+2] tricyclizations of enediyne and diynal substrates are also discussed. These newly discovered reactions can construct multiple bonds all at once, converting linear starting materials to polycyclic compounds in a single step. Thus, these new processes provide innovative routes to functionalized polycyclic compounds that are useful for the syntheses of natural and unnatural products.

Transition metals in organic synthesis: Highlights for the year 2005

“…Rhodium catalyzed a [2 + 2 + 2 + 1]cycloaddition of enediynes in the presence of a silane and carbon monoxide (Eq. (205)) [1028]. Cobalt and rhodium catalyzed a [5 + 1]cycloaddition of ethenylcyclopropanes with carbon monoxide to give 3-cyclohexen-1-ones (Eq.…”

Cationic Rhodium(I)/H8‐binap Complex Catalyzed [2+2+2] Cycloadditions of 1,6‐ and 1,7‐Diynes with Carbonyl Compounds

“…[8] For the rhodium-catalyzed reactions, [2+2+2+1] cycloadditions of diynals with CO by using a neutral rhodium(I) complex, [Rh(cod)Cl] 2 , as a catalyst furnished intramolecular [2+2+2] cycloaddition products as byproducts. [9] Carbonyl insertion into a cationic rhodacyclopentadiene was reported in cationic rhodium(I)/ biphep complex catalyzed carbonyl Z-dienylations through multicomponent reductive coupling of aldehydes and α-keto esters mediated by hydrogen in the presence of a catalytic amount of triphenylacetic acid, but this example is not the straightforward [2+2+2] cycloaddition of alkynes with carbonyl compounds. [10] Thus, a study concerning the [2+2+2] cycloaddition of diynes with carbonyl compounds by using a rhodium(I) complex as a catalyst has not been reported.…”

Intramolecular [2+2+2] Cycloaddition Reactions of Yne‐ene‐yne and Yne‐yne‐ene Enediynes Catalysed by RhI: Experimental and Theoretical Mechanistic Studies

“…Several transition-metal complexes have been reported as efficient catalysts in this process. [1][2][3] Among them, rhodium catalysts are becoming increasingly popular [4] especially in the enantioselective reaction in which [2+2+2] cycloaddition reactions of diynes and alkenes, [5] enynes and alkynes, [6] and enediynes [7] have been reported. Recently, Saµ and co-workers studied the cycloaddition reactions of a,w-diynes with alkenes by using a ruthenium complex as catalyst to give cyclohexadiene products.…”