The use of potassium persulfate enables an aerobic oxidation of benzyl substrates to provide aryl carbonyl compounds including acetophenones, benzophenones, imides, and benzoic acids under mild conditions in the presence of pyridine. Neither transition metals nor halogens are required as additives.
Y. Hu, L. Zhou, W. Lu, Synthesis, 2017, 49, 4007-4016.
Various aryl ketone derivatives react readily with DMSO under transition metal-free reaction condition, producing the α,β-unsaturated carbonyl compounds in good yields. This direct α-Csp3-H methylenation offers wide substrate scope and provides an efficient and expeditious approach to an important class of α,β-unsaturated carbonyl compounds.
Y.-F. Liu, P. Yi Ji, J.-W. Xu, Y.-Q. Hu, Q. Liu, W.-P. Luo, C.-C. Guo, J. Org. Chem., 2017, 82, 7161-7164.
A Fe-mediated decarboxylative cross-coupling reaction between α-oxocarboxylic acids and acrylic acids in aqueous solution provides an efficient and expeditious approach to α,β-unsaturated carbonyl compounds. This transformation offers a wide substrate scope and good functional group compatibility utilizing inexpensive and easily accessible reagents. Mechanism studies suggest that a free radical pathway is involved.
Q. Jiang, J. Jia, B. Xu, A. Zhao, C.-C. Guo, J. Org. Chem., 2015, 80, 3586-3596.
With K2S2O8 as the oxidant and AgNO3 as the catalyst, direct decarboxylative radical allylation of aliphatic carboxylic acids with allyl sulfones in aqueous CH3CN solution gave the corresponding alkenes in good yields under mild conditions. This site-specific allylation method exhibits wide functional group compatibility.
L. Cui, H. Chen, C. Liu, C. Li, Org. Lett., 2016, 18, 2188-2191.
A silver-promoted oxidative ring opening/alkynylation of cyclopropanols with ethynylbenziodoxolones (EBX) enables the formation of alkylated alkynes. Control experiments support a radical mechanism.
C.-Y. Wang, R.-J. Song, Y.-X. Xie, J.-H. Li, Synthesis, 2016, 48, 223-230.
With AgNO3 as the catalyst and K2S2O8 as the oxidant, an efficient and general method for the decarboxylative azidation of aliphatic carboxylic acids with tosyl azide or pyridine-3-sulfonyl azide in aqueous MeCN solution afforded the corresponding alkyl azides under mild conditions. A broad substrate scope and wide functional group compatibility were observed. A radical mechanism is proposed.
C. Liu, X. Wang, Z. Li, L. Cui, C. Li, J. Am. Chem. Soc., 2015, 137, 9820-9823.
In a catalytic decarboxylative nitrogenation, a series of tertiary, secondary, and primary organoazides were prepared from easily available aliphatic carboxylic acids by using K2S2O8 as the oxidant and PhSO2N3 as the nitrogen source via an alkyl radical process.
Y. Zhu, X. Liu, X. Wang, X. Huang, T. Shen, Y. Zhang, X. Sun, M. Zou, S. Song, N. Jiao, Org. Lett., 2015, 17, 4702-4705.
In the presence of AgNO3 as the catalyst and K2S2O8 as the oxidant, reactions of aliphatic carboxylic acids with (bpy)Cu(CF3)3 and ZnMe2 in aqueous acetonitrile at 40°C provide the corresponding decarboxylative trifluoromethylation products in good yield. The protocol is applicable to various primary and secondary alkyl carboxylic acids and exhibits wide functional group compatibility.
X. Tan, Z. Liu, H. Shen, P. Zhang, Z. Zhang, C. Li, J. Am. Chem. Soc., 2017, 139, 12430-12433.
Various anilides have been directly ortho-acetoxylated with acetic acid as the acetate source and K2S2O8 as the oxidant in the presence of Pd(OAc)2 as catalyst. The amide group is an elegant directing group to convert aromatic sp2 C-H bonds into C-O bonds.
G.-W. Wang, T.-T. Yuan, X.-L. Wu, J. Org. Chem., 2008, 73, 4717-4720.
A copper(II)-catalyzed oxidative cyclization of enamides gives oxazoles via vinylic C-H bond functionalization at room temperature. Various 2,5-disubstituted oxazoles bearing aryl, vinyl, alkyl, and heteroaryl substituents could be synthesized in good yields. This reaction protocol is complementary to a previously reported iodine-mediated cyclization of enamides to afford 2,4,5-trisubstituted oxazoles.
C. W. Cheung, S. L. Buchwald, J. Org. Chem., 2012, 77, 7526-7537.
A highly efficient method for the synthesis of oxazole derivatives from simple amides and ketones proceeds through a C-N bond formation followed by a C-O bond formation closing the ring. Because of the simple and readily available starting materials, easy operation, and high bioactivity of oxazoles, this strategy can be broadly applied to medicinal chemistry.
M. Zhang, L. Huang, H. Huang, X. Li, W. Wu, H. Jiang, Org. Lett., 2014, 16, 5906-5909.
A facile and practical TBAI-catalyzed reaction between N-tosyl hydrazones and sulfur provides 1,2,3-thiadiazoles in good yields under metal-free conditions. This procedure serves as an improvement for the Hurd-Mori reaction.
J. Chen, Y. Jiang, J.-T. Yu, J. Cheng, J. Org. Chem., 2016, 81, 271-275.
An efficient and versatile Pd(II)-catalyzed oxidative three-component cascade reaction of diverse amines, alkyne esters, and alkenes enables the direct synthesis of diverse 2,3,4-trisubstituted pyrroles with broad functional group tolerance and in good to excellent yields.
X. Zhang, X. Xu, G. Chen, W. Yi, Org. Lett., 2016, 18, 4864-4867.
A copper-catalyzed three-component reaction of methyl ketones, organic azides, and DMF as one-carbon (C1) donor provides 4-acyl-1,2,3-triazoles in good yields. The transformation proceeds via an oxidative C-H/C-H cross-dehydrogenative coupling followed by an oxidative 1,3-dipolar cycloaddition.
Y. Liu, G. Nie, Z. Zhou, L. Jia, Y. Chen, J. Org. Chem., 2017, 82, 9198-9203.
The use of K2S2O8 enables a nontransition metal-catalyzed synthesis of 2-aryl benzothiazoles through oxidative condensation of benzothiazoles with aryl aldehydes or phenylglyoxylic acids.
Z. Yang, X. Chen, S. Wang, J. Liu, K. Xie, A. Wang, Z. Tan, J. Org. Chem., 2012, 77, 7086-7091.
A fast and simple reaction of amidines gave benzimidazoles via iodine(III)-promoted oxidative C(sp3)-C(sp2) bond formation in nonpolar solvents, whereas the use of polar solvents favoured a C(sp2)-N bond formation to yield quinazolines. Further selective synthesis of quinazolines in polar solvent was realized using TEMPO as catalyst and K2S2O8 as the oxidant. No metal, base, or other additives were needed.
J.-P. Lin, F.-H. Zhang, Y.-Q. Long, Org. Lett., 2014, 16, 2822-2825.
A one-pot reaction cascade reaction enables a transition-metal-free construction of functionalized quinolines from readily available acetophenones and anthranils. The reaction involves in situ generation of α,β-unsaturated ketones from the acetophenone via one-carbon homologation by DMSO followed by the aza-Michael addition of anthranils and subsequent annulation. DMSO acts not only as solvent but also as one carbon source.
S. B. Wakade, D. K. Tiwari, P. S. K. P. Ganesh, M. Phanindrudu, P. R. Likhar, D. K. Tiwari, Org. Lett., 2017, 19, 4948-4951.
A silver-catalyzed method provides a practical, highly efficient, and straightforward route to substituted quinolin-2-ones or 3,4-dihydroquinolin-2-ones in one step through an intermolecular radical addition/cyclization in aqueous solution. A mechanism for the formation of quinolin-2-ones is proposed.
W.-P. Mai, G.-C. Sun, J.-T. Wang, G. Song, P. Mao, L.-R. Yang, J.-W. Yuan, Y.-M. Xiao, L.-B. Qu, J. Org. Chem., 2014, 79, 8094-8102.
An efficient metal-free tandem acylation/cyclization of alkynoates with aldehydes enables the synthesis of 3-acyl-4-arylcoumarins via addition of acyl radical to alkynes and a C-H bond functionalization to form two new C-C bonds simultaneously.
X. Mi, C. Wang, M. Huang, Y. Wu, Y. Wu, J. Org. Chem., 2015, 80, 148-155.
A transition-metal-free, K2S2O8-mediated intramolecular oxidative nitrogenation/oxygenation of C(sp3)-H in N-aryl benzylic amines followed by oxidation at the benzylic center provides an expedient access to quinazolin-4(3H)-ones, N-aryl-2-arylbenzimidazoles, and 4H-3,1-benzoxazin-4-ones.
J. K. Laha, K. S. S. Tummalapalli, A. Nair, N. Patel, J. Org. Chem., 2015, 80, 11351-11359.
An oxidative cross-dehydrogenative coupling (CDC) strategy enables an efficient acylation of quinolines and isoquinolines with arylmethanols as the acylating agents. This C-aroylation reaction was carried out in the presence of K2S2O8 as oxidant and methyltrioctylammonium chloride (Aliquat 336) as transfer agent in MeCN at 80°C under transition-metal-free conditions.
M. Adib, R. Pashazadeh, S. Rajai-Daryasarei, R. Kabiri, S. J. A. Gohari, , Synlett, 2016, 27, 2241-2245.
A scalable, direct functionalization of various quinones with several boronic acids proceeds readily at room temperature in an open flask using catalytic silver(I) nitrate in the presence of a persulfate co-oxidant. The scope with respect to quinones is broad, with a variety of alkyl- and arylboronic acids undergoing efficient cross-coupling.
Y. Fujiwara, V. Domingo, I. B. Seiple, R. Gianatassio, M. Del Bel, P. P. S. Baran, J. Am. Chem. Soc., 2011, 133, 3292-3295.
One-pot tandem Meyer-Schuster rearrangement of arylpropynols and successive radical cyclization with disulfides enables the synthesis of 2-sulfenylindenone derivatives in good yields. The reaction tolerates a number of functional groups.
X.-S. Zhang, J.-Y. Jiao, X.-H. Zhang, B.-L. Hu, X.-G. Zhang, J. Org. Chem., 2016, 81, 5710-5716.