Acid-catalyzed intramolecular ring-opening reactions of cyclopropanated oxabenzonorbornadienes with alcohol nucleophiles

Acid-Catalyzed Intramolecular Ring-Opening Reactions of Cyclopropanated Oxabenzonorbornadienes with Carboxylic Acid Nucleophiles

“…al. 12 General Procedure for the Dess-Martin reagent oxidation of alcohol-tethered CPOBDs to carboxylic acid-tethered CPOBDs: In a small flame-dried round bottom flask equipped with a stir bar, alcoholtethered cyclopropanated oxabenzonorbornadiene (1.0 equiv, 1.0 mmol) was dissolved in dry dichloromethane (5 mL/mmol). Dess-Martin reagent (1.4 equiv.)…”

“…The samples were ionized by electron ionization (EI) or positive electrospray ionization (ESI). Synthesis of the alcohol-tethered C5-and arylsubstituted cyclopropanated oxabenzonorbornadienes were prepared according to literature procedures from Wicks et al 12…”

“…1 H NMR (CDCl 3 , 400 MHz):  = 7.67 (d, J = 7.9 Hz, 1 H), 7.41 (dt, J = 1.5, 7.9 Hz, 1 H), 7.30 (dt, J = 1.2, 7.9 Hz, 1 H), 7.23 (d,J = 7.3 Hz,1 H),6.41 (dd,J = 3.5,12.2 Hz,1 H),6.30 (d,J = 1.3 Hz,1 H),1 H),5.37 (ddd,J = 1.3,4.4,12.2 Hz, 1 H), 3.12-3.04 (m, 1 H), 2.62-2.53 (m, 1 H).…”

“…11 Recently, our group investigated the intramolecular ring-opening reactions of CPOBD with alcohol nucleophiles under mild acid conditions to yield two regioisomeric products in good yields. 12 In this work, we report the first examples of acid-catalyzed intramolecular ring-opening of CPOBD 8 with carboxylic acid nucleophiles (Scheme 1). It was found that this reaction afforded two tricyclic regioisomers, labelled Type 3 product ( 9) and Type 2 product (10); however, the reaction was highly regioselective for the formation of the Type 3 product.…”