Facile acid catalyzed ring cleavage of N-acylated lactams

Chemoselective CaO‐Mediated Acylation of Alcohols and Amines in 2‐Methyltetrahydrofuran

“…[6] Esterification reactions in the absence of activators are not fully understood and have limited substrate scope (aromatic acid chlorides or compounds with a-acidic hydrogens are not used); this may be attributed to a considerable excess of the required acyl donor. [7] These limitations stimulated efforts to develop activators for improving the reactivity, among the most common are Brønsted acids (e.g., HCl, [8] p-TsOH [9] ) and Lewis acids (e.g., CeCl 3 , [10] MgBr 2 , [11] ZrCl 4 , [12] Sc(OTf) 3 , [13] LiClO 4 , [14] Mg(ClO 4 ) 2 [15] ). These acids cannot be used in the presence of acid-sensitive substrates, thus reducing their real usefulness.…”

Acid-Mediated C–N Bond Cleavage in 1-Sulfonylpyrrolidines: An Efficient Route towards Dibenzoxanthenes, Diarylmethanes, and Resorcinarenes

“…Other examples include iron-mediated С-N bond cleavage in N-nosylprolines, 22 silver oxide catalyzed Arndt-Eistert reaction of N-tosylproline, 23 synthesis of the aminoalcohols via Baeyer-Villiger oxidation of N-tosylpyrrolidine, and treatment of intermediate products with LiAlH 4 . 7,8 Although different from the abovementioned examples, the ammonolysis, 24 hydrolysis, 25 and alcoholysis 26 of N-sulfonyl γ-lactams should also be mentioned. Most of these methods require harsh reaction conditions and usage of either air-sensitive or expensive reagents.…”

Cleavage of Activated Cyclic Amines: Unprecedented Approach toward 2-Substituted Cyclobutanones

“…As anticipated, the rearrangement occurred smoothly and we describe our results in this Letter. Very few examples of rearrangements or fragmentations of the activated five-membered ring are known …”