Synthesis of 1,3‐Cycloalkadienes from Cycloalkenes: Unprecedented Reactivity of Oxoammonium Salts

Abstract

Fewm ethods allowf or the direct conversion of cycloalkenes into cycloalkadienes with high chemo-and regioselectivity. Herein, we report ac onvenient one-pot process for this transformation that involves the unprecedented N-preferential group transfer of N-oxoammonium salts to cycloalkenes,f ollowed by Cope elimination, to affordcycloalkadienes at room temperature and pressure. Scheme 4. Dibromination-dehydrobromination sequence. Scheme 5. Functionalization of the obtained 1,3-cyclohexadienes. Boc = tert-butoxycarbonyl, NMO = 4-methylmorpholine N-oxide, TPP = 5,10,15,20-tetraphenylporphyrin, Ts = toluenesulfonyl.

4‐Chloro‐2‐azaadamantane N‐Oxyl (4‐Cl‐AZADO): A Readily Preparable Organocatalyst for NOx Co‐catalyzed Aerobic Alcohol Oxidation

“…Initially, various 4‐substituted AZADO derivatives were synthesized (Scheme 2). On the basis of the report by Staas and Spurlock, N ‐Cbz‐4‐substituted‐2‐azaadamantanes 6 were easily obtained from 5 in high yields by using halogenating reagents such as Selectfluor® (for 6 a ), trichloroisocyanuric acid (TCCA, for 6 b ), [8] N ‐bromosuccinimide (NBS, for 6 c ), or epoxidation with m ‐chloroperbenzoic acid ( m CPBA) [7] followed by methylation (for 6 d ), respectively. The deprotection of the Cbz group and the oxidation of the resulting secondary amine afforded various 4‐substituted AZADOs 7 .…”

“…The deprotection of the Cbz group and the oxidation of the resulting secondary amine afforded various 4‐substituted AZADOs 7 . 4‐F‐AZADO ( 7 a ) and 4‐Cl‐AZADO ( 7 b ) [8] were synthesized in good yields, unlike 4‐Br‐AZADO ( 7 c ) and 4‐MeO‐AZADO ( 7 d ).…”

On the Reaction Mechanism of the Selective C(sp3)–H Functionalization of N-Benzylpiperidines Mediated by TEMPO Oxoammonium Cation

“…1 2 However, its use for the C–H oxidation of amines, particularly in cyclic amines, has been practically limited to either benzylic or allylic amines. 3 In this regard, during the last six years our research group has developed, from simple saturated tertiary cyclic amines and under transition-metal-free conditions, a series of C–H oxidation reactions of cyclic amines to bioactive alkaloids or advanced alkaloid intermediates. 4 These strategies are grounded on a selective and dual C(sp 3 )–H functionalization of tertiary piperidines and pyrrolidines mediated by TEMPO and sodium oxychloride reagents (NaClO 2 and NaClO).…”

Selective α‐Oxyamination and Hydroxylation of Aliphatic Amides

“…Zuschriften Fort hese two cases,w eb elieve that the generated carbon radical intermediates are very active and quickly couple with the excess amount of the persisitant TEMPO radical. In addition, we assumed that the TEMPO + salt [17] generated in situ through the disproportionation reaction with iPr 3 SiOTf,is more reactive and might be the key intermediate in this transformation. This hypothesis also reasonably explains the requirement of more than 2.0 equivalents of TEMPO and iPr 3 SiOTf in this oxidative C À Hb ond oxyamination of the amides.T herefore,t he TEMPO + OTf À salt [18] was prepared and used in the control experiment with 1a.T oo ur delight, the target product 2awas obtained in 64 %yield (Scheme 6c).…”