Enantioselective Synthesis of Planar Chiral Paracyclophanes with Short ansa Chains and Structure of Strained Dioxa[7]paracyclophane

Abstract

I. General Anhydrous CH 2 Cl 2 (No. 27,099-7) was obtained from Aldrich and used as received. Segphos, H 8-BINAP, xyl-H 8-BINAP, and DTBM-Segphos were obtained from Takasago International Corporation. [Rh(cod) 2 ]BF 4 was obtained from Umicore. Diynes 1a-e were already reported in the literatures. 1 All other reagents were obtained from commercial sources and used as received. II. Enantioselective Synthesis of Paracyclophanes Typical procedure (Table 2, entry 1): Under an argon atmosphere, (S)-H 8-BINAP (15.8 mg, 0.0250 mmol) and [Rh(cod) 2 ]BF 4 (10.2 mg, 0.0250 mmol) were dissolved in CH 2 Cl 2 (2.0 mL) and the mixture was stirred at r.t. for 30 min. H 2 was introduced to the resulting solution in a Schlenk tube. After stirring at r.t. for 1.5 h, the resulting mixture was concentrated to dryness. To a CH 2 Cl 2 (20 mL) solution of the residue was added a CH 2 Cl 2 (5.0 mL) solution of 1a (76.1 mg, 0.500 mmol) and 2a (42.0 mg, 0.500 mmol) at r.t. over 2 min. After stirring at r.t. for 1 h, the resulting mixture was concentrated and purified on a preparative TLC (n-hexane/ethyl acetate = 1:1), which furnished (R)-(+)-3aa (21.6 mg, 0.0914 mmol, 18% yield, 75% ee). (R)-(+)-2,6-Dioxa[7]paracyclophane-9-carboxymethylate [(+)-3aa] (Table 2, entry 1) O O MeO 2 C

Stereoselective synthesis of [2.2]triphenylenophanesviaintramolecular double [2 + 2 + 2] cycloadditions

“…On the other hand, Rh-catalyzed [2 + 2 + 2] cycloadditions 16–18 allow enantioselective control of the planar chirality of [ n ]cyclophanes. 19 Here, we report the stereoselective synthesis of oxamethylene-bridged PAHs-based [2.2]cyclophanes ([2.2]triphenylenophanes) 3 via the base-mediated intermolecular macrocyclization of triynes 1 , leading to cyclic hexaynes 2 , and the subsequent Rh- or Ni-catalyzed intramolecular double [2 + 2 + 2] cycloadditions 20–22 (Fig. 1d).…”