1,3‐Difunctionalization of Aminocyclopropanes via Dielectrophilic Intermediates

Abstract

We report an oxidative ring-opening strategy to transform acyl, sulfonyl or carbamate protected aminocyclopropanes into 1,3-dielectrophilic carbon intermediates bearing ah alide atom (Br,I )a nd aN ,O-acetal. Replacing the alkoxy group of the N,O-acetal can be achieved under acidic conditions through an elimination-addition pathway, while substitution of the halides by nucleophiles can be done under basic conditions through aS N 2p athway,g enerating aw ide range of 1,3-difunctionalized propylamines.Aproof of concept for asymmetric induction was realized using ac hiral phosphoric acid (CPA) as catalyst, highlighting the potential of the method in enantioselective synthesis of important building blocks.Scheme 1. A) Our previous work with D-A aminocyclopropanes.B ) Bioactive compounds featuring a,g-difunctionalized amines. C) Hofmann-Lçffler-Freytag reaction. D) This work:o xidative ring opening strategy towards a,g-difunctionalized amines.

Hypervalent‐Iodine‐Mediated Carbon–Carbon Bond Cleavage and Dearomatization of 9H‐Fluoren‐9‐ols

“…Herein we report a domino reaction mediated by hypervalent iodine for the synthesis of spiro‐ethers from 9 H ‐fluoren‐9‐ols (Scheme c) . It features an unprecedented aryl−C(sp 3 ) bond cleavage promoted by hypervalent iodine, and the mechanism might be different from the metal‐promoted β‐elimination or radical β‐scission discussed above.…”

“…[8] Herein we report ad omino reaction mediated by hypervalent iodine for the synthesis of spiro-ethers from 9Hfluoren-9-ols (Scheme 1c). [9][10][11] It features an unprecedented arylÀC(sp 3 )b ond cleavage promoted by hypervalent iodine, and the mechanism might be different from the metalpromoted b-elimination or radical b-scission discussed above. Ther ing-opening products quickly underwent oxidative dearomatization/cyclization to produce an oxo-spiro scaffold.…”

“…At last, commonly used oxidants were investigated. PIDAa nd PIFAp roduced acceptable yields of 2a.H owever,H 2 O 2 and m-CPBAg ave unknown mixtures,w hile NaIO 4 was an ineffective oxidant (entries [9][10][11][12][13].…”

Deconstructive Oxygenation of Unstrained Cycloalkanamines

“…For example, the groups of Zard, Leonori, Xiao, and Guo have developed iminyl‐radical‐mediated ring‐opening of strained rings by using either oxime esters or ethers as the substrates (Scheme b). Meanwhile, the groups of Zheng– and Waser have independently reported ring‐opening reconstruction and functionalization of strained cyclopropylamines and cyclobutylamines. However, different from alkoxyl radicals, those reactions are limited to strained rings, while the ring‐opening of unstrained rings remains a challenge.…”

An Approach to α‐ and β‐Amino Peroxides via Lewis Acid Catalyzed Ring Opening‐Peroxidation of Donor‐Acceptor Aziridines andN‐Activated Aziridines

“…A protocol based on Curtius rearrangement was developed by Dussault where peroxyalkanoyl azides were transformed into α‐ N ‐peroxide moiety . Another recent report from Waser's group showcased selected entries to N , O ‐peroxyacetal from aminocyclopropanes via oxidative ring‐opening strategy with hydroperoxides …”