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Synthesis of Diaryl Ketones through Oxidative Cleavage of C#C Double Bonds in N-Sulfonyl Enamides Hyunseok Kim, Sangjune Park, Yonghyeon Baek, Kyusik Um, Gi Uk Han, Da-Hye Jeon, Sang Hoon Han, and Phil Ho Lee J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b03068 • Publication Date (Web): 22 Mar 2018 Downloaded from http://pubs.acs.org on March 23, 2018
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The Journal of Organic Chemistry
Synthesis of Diaryl Ketones through Oxidative Cleavage of C‒C Double Bonds in N-Sulfonyl Enamides
Hyunseok Kim,† Sangjune Park,† Yonghyeon Baek, Kyusik Um, Gi Uk Han, Da-Hye Jeon, Sang Hoon Han, and Phil Ho Lee* Department of Chemistry, Kangwon National University, Chuncheon 24341, Republic of Korea E-mail:
[email protected] Table of Contents
ABSTRACT: An oxidative cleavage of C‒C double bond is developed from photochemical [2 + 2]-cycloaddition of diaryl N-tosyl enamides, aryl heteroaryl N-tosyl enamides, and N-tosyl cyclic enamides with singlet molecular oxygen followed by ring-opening reaction mediated by Cs2CO3 under air and sunlight without the use of photosesitizer, producing symmetrical and unsymmetrical diaryl, heterodiaryl, and cyclic ketones in good to excellent yields. Moreover, the oxidative cleavage of C‒C triple bonds from 1-alkynes is demonstrated for the synthesis of symmetrical and unsymmetrical ketones from Cu-catalyzed [3 + 2]-cycloaddition, Rh-catalyzed alkoxyarylation, photooxygenation, and ring-opening reaction in one-pot. Because synthesis of the symmetrical and unsymmetrical diaryl and/or heterodiaryl ketones bearing an electron-donating group is not easy, the present method is notable.
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INTRODUCTION Ketones have been recognized as one of the most significant and convertible functional groups in organic chemistry.1 Moreover, diaryl ketones are an element of an ordinary structural motif that is found in not only many natural products and biologically active compounds but also valuable building blocks and intermediates (Scheme 1).2
Scheme 1. Important Compounds Containing Diaryl Ketone Moiety HO
O
O
OH
OH O
O
O
OH
OH
Me
OH HO
OH Morintrifolins A
Monodictyphenone
OH O
OH
R
R
O MeO
OH
MeO
OMe OMe Phenstatin antineoplastic agent
R=
N
Me
N
Universal chirality sensor for amino acids
Accordingly, the development of various synthetic approaches to prepare diaryl ketones has been the important themes which have been investigated by many groups. To date, a number of synthetic methods for diaryl ketones have been reported and these methods can be generally divided into some categories (Scheme 2): Friedel-Crafts acylation of arenes with acid derivatives (eq 1),3 transition metal-catalyzed cross-coupling of organometallic species with carboxylic acid derivatives (eq 2),4 carbonylative cross-coupling of organometallic species with aryl halides (eq 3),5 crosscoupling of acyl anion equivalents with electrophiles (eq 4),6 oxidative cleavage of CðC double
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The Journal of Organic Chemistry
bond using oxidants7 and photooxygenation using singlet molecular oxygen (1O2) in the presence of photosensitizer (eq 5),8 oxidative CðC bond cleavage of aldehydes through visible light photoredox catalysis (eq 6),9 and metal-free oxidative CðC bond cleavage of aldehydes by O2 (10 atm) (eq 7).10
Scheme 2. Previously Reported Synthetic Methods for Diaryl Ketone
Recently, we reported a synthetic method for aryl azulenyl ketones through oxidative cleavage
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of the CðC double bond by the reaction of N-sulfonyl enamides having azulene moiety, which is nonbenzenoid aromatic compound, with cesium carbonate (Cs2CO3) without use of photosensitizer under air and natural sunlight (eq 8).11
In this regards, expansion of the limited scope of substrates bearing azulene motif are highly required. In our continuing efforts to develop the oxidative cleavage of CðC multiple bond, we envisioned that if a wide range of aromatic, heteroaromatic, and cyclic N-sulfonyl enamides were treated with base, the oxidative cleavage of the CðC double bond would take place to afford the valuable diaryl, aryl heteroaryl, and cyclic ketones. In addition, because synthesis of the symmetrical and unsymmetrical diaryl and/or heterodiaryl ketones bearing an electron-donating group is not easy, the development of efficient method is still very attractive and a significant challenge. Herein, we report an oxidative cleavage of C
