Catalytic Ring Expansion of Vinyl Oxetanes: Asymmetric Synthesis of Dihydropyrans Using Chiral Counterion Catalysis
作者:Boying Guo、Gregg Schwarzwalder、Jon T. Njardarson
DOI:10.1002/anie.201201367
日期:2012.6.4
Acid Showdown! The first catalyticring expansion of vinyl oxetanes to 3,6‐dihydro‐2H‐pyrans is described. Copper(II) triflate emerged as the best catalyst for this new transformation, which has broad scope as demonstrated by the eighteen examples included. The symmetric vinyl oxetane substrate can be asymmetrically desymmetrized when using either chiral Lewis or Brønsted acids as catalysts.
A novel and regioselective approach to carbonyl-containing alkylchlorides via silver-catalyzed ring-opening chlorination of cycloalkanols is reported. Concurrent C(sp3)–C(sp3) bond cleavage and C(sp3)–Cl bond formation efficiently occur with good yields under mild conditions, and the chlorinated products are readily transformed into other useful synthetic intermediates and drugs. The reaction features
Z-Selective ring opening of vinyl oxetanes with dialkyl dithiophosphate nucleophiles
作者:B. Guo、J. T. Njardarson
DOI:10.1039/c3cc46660d
日期:——
Dialkyl dithiophosphates selectively ring open vinyl oxetanes in excellent yields under mild reaction conditions to form useful allylic thiophosphate products with high Z-selectivity.