Highly Site-Selective Metal-Free C–H Acyloxylation of Stable Enamines

Abstract

A highly site-selective acyloxylation of stable enamines with PhI(OAc) under metal-free conditions to afford (E)-vinyl acetate derivatives in good to excellent yields is described. Depending on the judicious choice of the solvent system, either the α- or β-site-selective product could be obtained with high selectivity. For the α-site-selective product, the rearranged amide compound is obtained as the major product. This reaction proceeds under mild reaction conditions (room temperature, metal-free, and open-flask) and features a broad substrate scope.

PIDA‐Mediated Formal Olefinic C=C Bond Cleavage of α‐Oxo‐Ketene N,N‐Acetals toward Substituted Oxazolines

“…[13] Regarding iodo(III)-promoted oxidative transformations of amino-functionalized alkenes,Zhao and co-workersdeveloped aC ÀCb ond-forming strategy fori ndole synthesis through PIDA-mediated oxidizationo fN-aryl enamines (Scheme 1a). [14] Recently,L oh, Jiang and co-workers [15] reported highlys ite-selective CÀHa cyloxylation of enamines with PIDA, givings olvent-dependent a-a nd b-site-selective products (Scheme 1b). In as imilarm anner,s ynthesis of amides assisted by vicinala lkylthio migration of a-oxo-ketene N,S-acetals was achieved by our group (Scheme 1c).…”

Copper‐Catalyzed Regioselective Oxidative Cycloamidation of α‐[(β‐Dimethylamino)propenoyl]‐Alkylamides: Synthetic Route to Substituted Pyrrolidine‐2,4‐diones

“…Mediated by PIFA, α ‐[ β ‐(dimethylamino)propenoyl]‐alkylamide 1 is quickly converted into a fairly stable dihydrofuran‐3(2 H )‐one 2 , which is further oxidized by PIFA via a SET process to generate a cation radical A and iodanyl radical B ,. The cation A is captured by TFA to afford intermediate C ,–, acompanied by a ring‐opening reaction in the presence of transition metal halide to give a radical D ,. The latter couples with B forms intermediate E , which undergoes a cyclization to generate intermediate F , followed by a dehydrohalogenation to afford an intervening triflate G .…”

NBS‐Promoted C−H Amination of Enaminones for the Synthesis of N‐Heterocycle Substituted Enaminones**

“…These utilities continue to drive the interest in the development of new synthetic methodologies for synthesis of polyfunctionalized enaminones by direct C−H functionalization [5–13] . Hypervalent iodine reagents promoted umpolung reaction of enaminone represent a valuable tool to access multiple functionalized enaminones [5a–b,9b,10b] . As typical examples, Du's group reported a direct oxidative coupling for C(sp 2 )−N bond formation between enaminones and electron‐deficient amines in the presence of the combination of tert‐Butyl hydroperoxide (TBHP) and Tetrabutylammonium iodide (TBAI) (Scheme 1a) [14] .…”