An efficient protocol for the Pd-catalyzed regiospecific ortho-nitration of (E)-azoarenes has been achieved for the first time using tBuONO as a nitrating agent under atmospheric oxygen. A series of both symmetrical and unsymmetrical azoarenes were nitrated efficiently by this procedure providing excellent chemo- and regioselectivity and compatibility with a broad array of functional groups.
Efficient tandem ortho-C-H-amination/ipso-cyanation of iodoarenes was accomplished under a norbornene-mediated Pd-catalyzed process. A series of functionalized 2-aminobenzonitriles with much potential in the pharmaceutical industry were obtained by this protocol. This strategy was successfully employed for substitution with two cyano and four amino functionalities in an arene unit in one step under specified conditions.
A convenient and general protocol for oxidative arylation of vinyl arenes by aryl radicals generated in situ from arene diazonium fluoroborates promoted by ascorbic acid in air at room temperature has been developed in the absence of any additive and visible light irradiation. A series of diversely substituted 2-aryl acetophenones have been obtained in good yields by this procedure.
Palladium‐catalyzed oxidative CC cleavage of α‐hydroxyketones and 2‐aryl acetophenones in the presence of tert‐butyl hydrogen peroxide (TBHP) generates an acyl moiety, which promotes subsequent regioselective CH acylation producing a series of ortho‐acyl substituted symmetrical and unsymmetrical azoarenes. This protocol is successfully used for the synthesis of liver (X) receptor agonist.
Theb enzoxazine scaffolds are of much interesta st hey are found in al arge array of natural productsa nd pharmaceutical drugsw ith diverse activities.W eh aved eveloped ap alladium-catalyzed decarboxylative selectivem ono-and bis-acylation of 4H-benzo[d][1,3]oxazin-4-oned erivatives with a-oxo carboxylic acids via preferential cyclic imine-N-directed C À Ha ctivation.2 -Aryl-4H-benzo[d] [1,3]oxazin-4-one was acylated with av arietyo fs ubstitutedp henylglyoxylic acids to produce the corresponding products. It was observed that electron-donating groups (CH 3 ,O CH 3 )a ta ny position of the aromatic ring of phenylglyoxylic acid provided good to excellent yields,w hereasp henylglyoxylica cids containing electron-withdrawing groups (COCH 3 ,C N, NO 2 )g avet he productsi nm oderate yields.I nterest-ingly when the reactionw as performed with silver triflate (AgOTf) in place of silver nitrate (AgNO 3 ) in the presence of 4e quivalents of glyoxylic acid, the bis-acylated product was obtained together with as mall amount of mono-acylated product. This is the first report of acylation of 2-aryl-4H-benzo[d] [1,3]oxazin-4-ones via C À Ha ctivation. Then otable featureso ft his reactiona re acylation with more challenging heteroarene-oxo carboxylic acids and alkyl oxo carboxylic acids.T his new protocolp rovides an easy ande fficient access to av ariety of oacyl-4H-benzo[d][1,3]oxazin-4-one derivatives which are of pharmaceutical importance. Figure1.Af ew biologically active molecules containing the 4H-benzo[d][1,3]oxazin-4-onemoiety. Scheme2.C À Ha cylation of benzoxazine-4-ones with heteroarylglyoxylic acids. 286 asc.wiley-vch.de 2 016 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim Adv.Synth. Catal. 2016, 358,283 -295 FULL PAPERS Biju Majhi et al. Scheme 3. Pd-catalyzedC À Ha cylationo f2 -phenyl-4Hbenzo[d][1,3]oxazin-4-one with alkyl a-oxo carboxylic acids. Scheme 4. C À HAcylation of meta-substituted 2-aryl-4H-benzo[d][1,3]oxazin-4-ones.
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