Synthesis of Highly Functionalized Cyclohexenone Rings: Rhodium‐Catalyzed 1,3‐Acyloxy Migration and Subsequent [5+1] Cycloaddition

Abstract

Lead Rh‐ole: Highly substituted cyclohexenones were prepared from cyclopropyl‐substituted propargyl esters by using a [{Rh(CO)2Cl}2] catalyst. This metal catalyst promoted the 1,3‐acyloxy migration of propargyl esters and a subsequent [5+1] cycloaddition of the resulting allenylcyclopropanes in the presence of CO with high regioselectivity.

Synthesis of Functionalized Cyclohexenone Core of Welwitindolinones via Rhodium-Catalyzed [5 + 1] Cycloaddition

“…8,9 We examined the regioselectivity for the cleavage of the cyclopropane ring and found that the C-C bond adjacent to an electron-rich aryl group or away from a quaternary carbon was selectively cleaved. 8,10 This provided the basis for the proposed regioselective [5+1] cycloaddition of cyclopropanes 5 or 8 .…”

Rhodium-Catalyzed Carbonylative Synthesis of Heterocycles

“…Moreover, both of these cycloadditions involve a rhodium-catalyzed 1,2-acyloxy migration of propargyl esters which was reported in 1984 [159,160]. With some elegant work in this field [161][162][163], cyclopentenones can also be produced with the use of rhodium catalyst [Rh (COD)Cl] 2 (Scheme 51). Here, the acyloxy group in the propargyl ester starting material not only eliminates the need for the preformation of allenes but also provides a useful handle for further selective functionalization of the cyclopentenone products.…”

Interception of a Rautenstrauch Intermediate by Alkynes for [5+2] Cycloaddition: Rhodium‐Catalyzed Cycloisomerization of 3‐Acyloxy‐4‐ene‐1,9‐diynes to Bicyclo[5.3.0]decatrienes

“…We have previously shown that [{Rh(CO) 2 Cl} 2 ] is an efficient catalyst for the 1,3-acyloxy migration of propargyl esters. [11] Indeed, our preliminary study showed that product 9 could be obtained in 30-40 % yield with the catalyst [{Rh(CO) 2 Cl} 2 ]. Since this transformation has been carried out with the catalyst PtCl 2 , no further optimization was conducted.…”

“…[10] We recently found that [{Rh(CO) 2 Cl} 2 ] was able to catalyze the 1,3-acyloxy migration of propargyl esters in the synthesis of functionalized cyclohexenones. [11] The combination of this novel reactivity of Rh I in promoting acyloxy migration and its well-known capability to undergo facile oxidative addition, migratory insertion, and reductive elimination may offer many opportunities for the design of new reactions. We envisioned that a conceptually new approach to seven-membered rings was possible if intermediate 6 in the Rautenstrauch rearrangement could be intercepted by a tethered alkyne in a [5+2] cycloaddition under rhodium catalysis.…”

“…For example, if a carbene intermediate similar to 5 is generated, it may undergo cyclopropanation or cyclopropenation with alkenes or alkynes in the system. However, when substrate 7 a, available in four steps from 2-butene-1,4-diol, [20] was treated with a catalytic amount of [{Rh(CO) 2 [11][12][13].…”