Enantioselective Synthesis of Axially Chiral Styrene‐Carboxylic Esters by Rhodium‐Catalyzed Chelation‐Controlled [2+2+2] Cycloaddition

Abstract

Axially chiral styrene‐carboxylic esters were synthesized in high yields with excellent enantioselectivity by the cationic rhodium(I)/H8‐BINAP complex‐catalyzed chelation‐controlled [2+2+2] cycloaddition reactions of 1,6‐ and 1,7‐diynes with 1,3‐enyne‐carboxylic esters. The diastereo‐ and enantioselective synthesis of C2 symmetric axially chiral cis and trans‐stilbene‐dicarboxylic esters was also achieved by the double [2+2+2] cycloaddition reactions of two molecules of the 1,6‐diyne with 2,3‐dialkynylmaleate and 2,3‐dialkynylfumarate, respectively. In these reactions, the 1,3‐enyne‐carboxylic esters coordinating to rhodium with a five‐membered chelate were more reactive than those coordinating to rhodium with a six‐membered chelate, although both chelation modes realized excellent enantioselectivity. The enantioselection mechanism of the cationic rhodium(I)‐catalyzed chelation‐controlled [2+2+2] cycloaddition was elucidated by DFT calculations.

Rhodium‐Catalyzed Chemo‐, Regio‐, Diastereo‐, and Enantioselective Intermolecular [2+2+2] Cycloaddition of Three Unsymmetric 2π Components

“…On the basis of these results, a plausible mechanism for the three-component [2+2+2] cycloaddition is shown in Scheme 5b. [15][16][17] Terminal alkynes 1 a and 1 g and enamide 2 d react with the cationic rhodium to give enamide-…”

Room Temperature Fluoranthene Synthesis through Cationic Rh(I)/H8-BINAP-Catalyzed [2 + 2 + 2] Cycloaddition: Unexpected Acceleration due to Noncovalent Interactions

“…In addition to the RhCl­(PPh 3 ) 3 catalyst, our research group has reported that cationic Rh­(I)/biaryl bisphosphine complexes are highly effective catalysts for the [2 + 2 + 2] cycloadditions of 1,6-diynes with alkynes, nitriles, and isocyanates under mild conditions. Here we report the cationic Rh­(I)/H 8 -BINAP complex-catalyzed [2 + 2 + 2] cycloaddition using 1,8-dialkynylnaphthalenes, giving substituted fluoranthenes and azafluoranthenes at room temperature (Figure c, below).…”

Ir/Zn-cocatalyzed chemo- and atroposelective [2+2+2] cycloaddition for construction of C─N axially chiral indoles and pyrroles

“…Transition metal-catalyzed [2+2+2] cycloaddition of three 2π components has attracted much attention, due to its high efficiency and atom economy for the rapid construction of functionalized sixmembered carbo-and heterocycles with high functional group tolerance (1)(2)(3). In particular, transition metal-catalyzed inter-and intramolecular asymmetric [2+2+2] cycloadditions of alkynes have been proven as a powerful tool to synthesize valuable benzenebased skeletons bearing central (4,5), axial (6)(7)(8)(9), planar (10,11), helical chirality (12)(13)(14)(15)(16), and chiral belts (17)(18)(19), which were well established by Tanaka and others (Fig. 1A).…”