Pd(II)-Catalyzed Allylic C–H Amination for the Preparation of 1,2- and 1,3-Cyclic Ureas

A general synthesis of 1,2- and 1,3-cyclic ureas is accomplished by intramolecular allylic C–H amination employing Pd­(TFA)₂/bis-sulfoxide as a catalyst. By careful modification of substrates and catalyst, a variety of 1,2-cyclic ureas are accessible from not previously employed terminal olefins substituted in allylic or vinylic positions. Furthermore, MS4A is found to be an effective additive for the synthesis of 1,3-cyclic ureas in good yields and excellent diastereoselectivities

Chiral Pyridinium Phosphoramide as a Dual Brønsted Acid Catalyst for Enantioselective Diels–Alder Reaction

Chiral pyridinium phosphoramide <b>1·HX</b> was designed to be a new class of chiral Brønsted acid catalyst in which both the pyridinium proton and the adjacent imide-like proton activated by the electron-withdrawing pyridinium moiety could work cooperatively as strong dual proton donors. The potential of <b>1·HX</b> was shown in the enantioselective Diels–Alder reactions of 1-amino dienes with various dienophiles including <i>N</i>-unsubstituted maleimide, which has yet to be successfully used in an asymmetric Diels–Alder reaction

Metal Template Assisted Proximal Arrangement of a Nucleophile and an Electrophile: Site-Selective Acylation of α‑Hydroxyamides in Polyols

Site-selective acylation of α-hydroxyl groups in amides has been achieved in the presence of other primary hydroxyl groups with intrinsic high reactivity. In this methodology, a relatively stable pyridine aldoxime ester was exploited as an acyl donor to suppress undesired acylation. The catalytic activation of a pyridine aldoxime ester with a Lewis acid produced a cationic complex, which preferentially attracted the Lewis basic α-hydroxyamide via a template effect, to thus facilitate <i>o</i>-acylation