Catalytic Enantioselective Synthesis of Planar Chiral Cyclophanes

Abstract

The catalytic enantioselective synthesis of planar chiral cyclophanes has been achieved by two types of transition-metal catalysis: (1) enantioselective construction of aromatic rings by transition-metal-catalyzed [2+2+2] cycloaddition reactions; (2) enantioselective construction of ansa chains by transitionmetal-catalyzed coupling reactions. The former approach has been achieved by the cationic rhodium(I)/H 8 -BINAP complexcatalyzed enantioselective intramolecular [2+2+2] cycloaddition of triynes, which afforded planar chiral dioxa [6][12]-metacyclophanes with high ee values, although the yields were low. Planar chiral carba [10][12]paracyclophanes could also be synthesized with high yields and ee values by the cationic rhodium(I)/BDPP complex-catalyzed enantioselective intermolecular [2+2+2] cycloaddition of cyclic diynes with monoynes. On the other hand, the latter approach was achieved by the cationic rhodium(I)/BINAPHANE or palladium(II)/BINAP complex-catalyzed double CS bond formation between dithiols and 1,4-bis(bromomethyl)benzenes, which afforded planar chiral dithia [9][12]paracyclophanes and dithia[3.3]paracyclophanes with varying yields and ee values.

Enantioselective Synthesis of Planar Chiral Zigzag-Type Cyclophenylene Belts by Rhodium-Catalyzed Alkyne Cyclotrimerization

“…Importantly, its helical chirality was stable because this Möbius belt was doubly stranded and no racemization proceeded even at elevated temperature. For the enantioselective synthesis of planar chiral cyclic π-conjugated molecules, , Isobe synthesized singly stranded cyclochrysenylenes, that possess a stable planar chirality due to large ring strain, by using an excess amount of cholesteryl stearate, although the product ee values were low (11–17%) . However, the enantioselective synthesis of planar chiral cyclic π-conjugated molecular belts has not been achieved to date.…”

Chiral isothiourea-catalyzed kinetic resolution of 4-hydroxy[2.2]paracyclophane

“…Accordingly, the development of methods for the asymmetric synthesis of enantiomerically pure, or at least enantiomerically enriched, derivatives that can be utilized as building blocks for more demanding ligands and catalysts became a task of high importance. Thus, several strategies to access enantioenriched [2.2]paracyclophanes have been reported, either relying on classical resolution approaches or, more recently, making use of asymmetric catalysis to carry out kinetic resolutions of easily accessed racemic precursors [ 3 – 4 13 – 15 ]. 4-Hydroxy[2.2]paracyclophane ( 2 ) is one of the commonly used building blocks, which is easily accessible in a racemic manner starting from 1 according to nowadays well-established procedures [ 16 – 18 ].…”

Leveraging Fluorescent Emission to Unitary Yield: Dimerization of Polycyclic Aromatic Hydrocarbons

“…[1][2][3][4][5][6][7] Key examples include synthetic bacteriochlorins, [8] mesoÀ meso linked porphyrins, [2] extended naphthofurans, [4] [9] and binaphthyl-derived polymers. [3] [10] Among the different scaffolds, biaryls and its derivatives have certainly attracted the widest interest, as they can be used as ligands for asymmetric catalysis, [11][12][13][14] key structural elements in pharmacologically active substances, [15][16][17] agrochemicals, [17] [18] supramolecular architectures, [19][20][21][22][23][24][25][26] mechanophoresbased sensors, [27] [28] and light-harvesting complexes, [29] [30] to mention a few. In this context, chiral 1,1'-bi-2naphthols (BINOLs) revealed to be a versatile building block for the construction of functional luminescent materials for fluorescent sensors, [31][32][33][34][35][36][37] metal organic frameworks (MOFs), [22] [38] chiral polymers, [10][31]…”