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Acetophenone ring closure

Joel K Annor-Gyamfi, Krishna Kumar Gnanasekaran, Richard A Bunce
An efficient route to substituted 1-aryl-1 H -indazoles has been developed and optimized. The method involved the preparation of arylhydrazones from acetophenone or benzaldehyde substituted by fluorine at C2 and nitro at C5, followed by deprotonation and nucleophilic aromatic substitution (SN Ar) ring closure in 45-90%. Modification of this procedure to a one-pot domino process was successful in the acetophenone series (73-96%), while the benzaldehyde series (63-73%) required a step-wise addition of reagents...
March 16, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Guo-Qiang Chen, Fatma Türkyilmaz, Constantin G Daniliuc, Christoph Bannwarth, Stefan Grimme, Gerald Kehr, Gerhard Erker
The dienylborane 2a was prepared by regioselective alkyne hydroboration of the conjugated enyne 1a with Piers' borane [HB(C6F5)2]. Its reaction with a series of acetophenone derived enamines 3 resulted in the formation of the strong enamine β-carbon adduct with the borane Lewis acid (4). In contrast B-C adduct formation between the dienylborane 2a and a series of much more bulky cyclohexanone derived enamines (6) is rapidly reversible above ca.-30 °C and then leads to the formation of the [4 + 2]cycloaddition products 8...
November 14, 2015: Organic & Biomolecular Chemistry
Yulong Kuang, Yan Lu, Yu Tang, Xiaohua Liu, Lili Lin, Xiaoming Feng
The asymmetric Darzens reaction between phenacyl bromides and N-protected isatins was developed to synthesize potentially bioactive spiro-epoxyoxindoles. The optically active products were obtained in moderate to good yields and enantioselectivities catalyzed by chiral N,N'-dioxide-Co(acac)2 complexes. A retro-aldol process accompanying the ring-closure step was observed in the process. A chiral control step was determined to be the initial aldol addition.
August 15, 2014: Organic Letters
John C Walton
Selective syntheses are now available for compounds of many classes, based on C-centered radicals, exploiting a diverse range of mechanisms. The prospect for chemistry based around N- and O-centered radicals is probably more favorable because of the importance of heterocycles as biologically active materials. Heteroradical chemistry is still comparatively underdeveloped due to the need for safe and easy ways of generating them. Oxime esters appeared promising candidates to meet this need because literature reports and our EPR spectroscopic examinations showed they readily dissociated on photolysis with production of a pair of N- and O-centered radicals...
April 15, 2014: Accounts of Chemical Research
Anabha E Raveendran, Rony Rajan Paul, Eringathodi Suresh, Vijay Nair
Nucleophilic heterocyclic carbenes (NHCs) have been used for the first time as catalysts in the cyclopropanation of ethyl cyanocinnamates with phenacyl bromide by Michael-initiated ring-closure (MIRC).
February 21, 2010: Organic & Biomolecular Chemistry
Mousa Al-Smadi, Samer Ratrout
The aromatic polyketones 3a-d are versatile compounds for the synthesis of the multi-1,2,3-selenadiazole aromatic derivatives 1a-d. The preparation starts with the reaction between the multi-bromomethylene benzene derivatives 2a-d and 4-hydroxy- acetophenone to give compounds 3a-d which are transformed through the reaction with semicarbazide hydrochloride or ethyl hydrazine carboxylate into the corresponding semicarbazones derivatives 4a-d or hydrazones 5a-d. The reaction with selenium dioxide leads to regiospecific ring closure of semicarbazones or hydrazones to give the multi- 1,2,3-selenadiazole aromatic derivatives in high yield...
2005: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
John M Keith, Leslie A Gomez, Ronald L Wolin, Ann J Barbier, Sandy J Wilson, Jamin D Boggs, Curt Mazur, Ian C Fraser, Brian Lord, Leah Aluisio, Timothy W Lovenberg, Nicholas I Carruthers
A series of novel and potent pyrrolidino-tetrahydroisoquinolines with dual histamine H(3) antagonist/serotonin transporter inhibitor activity is described. A highly regio- and diastereoselective synthesis of the pyrrolidino-tetrahydroisoquinoline core involving acid mediated ring-closure of an acetophenone intermediate followed by reduction with NaCNBH(3) was developed. In vitro and in vivo data are discussed.
May 1, 2007: Bioorganic & Medicinal Chemistry Letters
John M Keith, Leslie A Gomez, Michael A Letavic, Kiev S Ly, Jill A Jablonowski, Mark Seierstad, Ann J Barbier, Sandy J Wilson, Jamin D Boggs, Ian C Fraser, Curt Mazur, Timothy W Lovenberg, Nicholas I Carruthers
A series of tetrahydroisoquinolines acting as dual histamine H3/serotonin transporter ligands is described. A highly regio-selective synthesis of the tetrahydroisoquinoline core involving acid mediated ring-closure of an acetophenone intermediate followed by reduction with NaCNBH3 was developed. In vitro and in vivo data are discussed.
February 1, 2007: Bioorganic & Medicinal Chemistry Letters
Jotham W Coe, Krista E Bianco, Brian P Boscoe, Paige R Brooks, Eric D Cox, Michael G Vetelino
Oxidative ring closure of alkyl-substituted 2-hydroxyacetophenone trifluoromethanesulfonate esters (triflates) occurs upon exposure to base in anaerobic DMF at 20-90 degrees C. Alkyl substitution is required for ring closure. A migrated enol triflate product forms at lower temperature in high yield via migration of the trifluoromethanesulfonate in the unsubstituted and monoalkyl-substituted cases. The alkyl-substituted enol triflates also enter into the benzofuran-3-one ring-forming process under thermal cyclization conditions...
December 26, 2003: Journal of Organic Chemistry
Spivey, Diaper, Adams
An efficient synthesis of chlorogermane linker 12 is described. Economic introduction of germanium into this linker is accomplished by insertion of dichlorogermylene [from germanium(IV) chloride] into the homobenzylic C-Cl bond of 4-(2-chloroethyl)phenol 1. Using linker 12, transmetalation with lithiated 4-acetophenone, 3-acetophenone, and 4-(4'methoxy)biphenyl followed by Mitsunobu-type coupling to Argogel gives functionalized resins 14, 16, and 18, respectively. Treatment of resin 18 with TFA, ICl, Br2, or NCS effects clean ipso-degermylation releasing biphenyls 19-22, respectively...
August 25, 2000: Journal of Organic Chemistry
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