Asymmetric Synthesis of Protected Cyclohexenylamines and Cyclohexenols by Rhodium‐Catalyzed [2+2+2] Cycloaddition

Abstract

It has been established that cationic rhodium(I)/axially chiral biaryl bis(phosphine) complexes catalyze the asymmetric [2+2+2] cycloaddition of 1,6-enynes with electron-rich functionalized alkenes, enamides, and vinyl carboxylates, to produce the corresponding protected cyclohexenylamines and cyclohexenols. Interestingly, regioselectivity depends on structures of substrates. The present cycloaddition was successfully applied to the enantioselective total synthesis of (-)-porosadienone by using the amide moiety as a leaving group.

Rhodium‐Catalyzed Asymmetric [2+2+2] Cycloaddition of 1,6‐Enynes with Racemic Secondary Allylic Alcohols through Kinetic Resolution

“…Not only acrylamides but also enamides and oxabenzonorborna‐dienes could be employed in the rhodium‐catalyzed asymmetric [2+2+2] cycloaddition with 1,6‐enynes. In the reactions using acrylamides and enamides, the coordination of the amide carbonyl into rhodium induce high reactivity and selectivity, and suppress the undesired β‐hydrogen elimination giving diene products …”

The intermolecular hydro-oxycarbonylation of internal alkynes: current state of the art

“…Enol ester derivatives represent a relevant class of compounds widely used as mild acylating reagents, [1][2][3][4] as monomers for the production of diverse types of polymers and copolymers, [5][6][7][8] and as starting materials in a large variety of reactions, including asymmetric hydrogenation, [9][10][11][12] cycloaddition, [13][14][15][16] cyclization, [17][18][19][20] hydroformylation, [21][22][23] cross-coupling, [24][25][26][27] Michael addition, [28][29][30][31] aldol-type, [32][33][34] Mannich-type 35 and amide bond-forming processes, 36 to name a few. The enol ester motif is also found in a number of natural products with relevant biological properties.…”

Rhodium‐Catalyzed Asymmetric [2+2+2] Cycloaddition Reactions of 1,6‐Enynes and Oxabenzonorbornadienes

“…[4] By using activated alkenes instead of alkynes, the group of Tanaka has accomplished the produce of chiral substituted cyclohexenes. [5] In 2017, the group of Tenaglia has developed a neutral ruthenium catalyst to enable the asymmetric [2 + 2 + 2] cycloadditions of 1,6-enynes with alkynes. [6] Hetero-bicyclic alkenes are valuable synthetic intermediates and useful building blocks in molecular architecture as they can serve as a general template to create highly substituted ring systems with mutiple chiral centers.…”

“…On the basis of the reported literatures, [4][5][6] a proposed mechanism for this novel asymmetric [2 + 2 + 2] cycloaddition reaction is outlined in Figure 4. The catalytic cycle is initiated by the reaction between the chiral rhodium complex and 1,6-enyne 1 a to provide the complex B, which is transformed into the rhodacyclopentene species C by cyclo-isomerization.…”