Organocatalytic Enantioselective α‐Amination by Conjugate Addition of 5H‐Thiazol‐4‐ones to Arylazocarboxylates: Access to Chiral N,S‐acetals

Abstract

A chiral phosphoric acid catalyzed stereoselective Michael addition of 5H‐thiazol‐4‐ones to arylazocarboxylates was developed for the construction of optically active N,S‐acetal frameworks. Both 1‐naphthylazocarboxylates and phenylazocarboxylates were compatible to afford a series of 1,4‐adducts in generally high yields and enantioselectivities. Notably, the catalytic protocol enables the formation of N,S‐acetals featuring thiazol‐4‐one skeleton.

Study of microstructure and mechanical properties of friction stir welded ferrite-martensite DP700 steel

“…The force to align the rods and flakes is a configuration force derived from the thermodynamics [13]. The initial notification of the alignment effect of the passing electric current in a matrix with submerged objects can be traced back to 30 years ago where an experiment shows that the growing of crystals in liquid metal has been elongated along the direction of electric field by the passing electric field [14]. This is again noticed in our own experiments that the shape of inclusions has been changed toward the electric field direction during the solidification of liquid steel [15].…”

Organocatalytic Enantioselective 1,10-Addition of Alkynyl Indole Imine Methides with Thiazolones: An Access to Axially Chiral Tetrasubstituted Allenes

“…In particular, propargylic alcohols were successfully applied to in situ form conjugate systems under acidic conditions, − , followed by asymmetricorganocatalytic additions for the construction of axially chiral tetrasubstituted allenes . Based on our previous work on organocatalytic asymmetric construction of axially chiral tetrasubstituted allenes, ,,, and as a part of our ongoing interest in the field of organocatalytic remote stereocontrolled reactions , and construction of sulfur-containing tetrasubstituted carbon stereocenters, herein we disclose a CPA-catalyzed asymmetric 1,10-conjugate addition of alkynyl indole imine methides formed in situ from α-(6-indolyl)­propargylic alcohols for the construction of axially chiral tetrasubstituted allenes (Scheme F) . However, several challenges have to be considered: (1) an imine methide intermediate might be generated as a Z / E mixture in terms of the double bond, which would influence regio-, diastereo-, and enantioselectivities; (2) 1,8-addition needs to be suppressed to avoid undesired byproducts; (3) solving the strong coordinating and adsorptive properties of sulfur species; (4) an appropriate catalytic system should be selected to control the regio-, diastereo-, and enantioselectivities effectively.…”