Synthesis, Table of Contents Synthesis 2018; 50(18): 3723-3730DOI: 10.1055/s-0037-1610439 paper © Georg Thieme Verlag Stuttgart · New York Regioselective Synthesis of Dihydro-1H-furo[b]indol-1-ones and Their Carbanionic Reactivity Supriti Jana Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 India, Email: dmal@chem.iitkgp.ernet.in , Mausumi Bandyopadhyay Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 India, Email: dmal@chem.iitkgp.ernet.in , Dipakranjan Mal * Department of Chemistry, Indian Institute of Technology Kharagpur, 721302 India, Email: dmal@chem.iitkgp.ernet.in › Author Affiliations Recommend Article Abstract Buy Article All articles of this category Abstract A general synthesis of 3,4-dihydro-1H-furo[b]indol-1-ones, representing a furanone-fused pyrrole unit, has been developed. The dehydrohalogenative cyclization of 4-aminofuranones was achieved by reaction with Pd(OAc)2 and DABCO in DMF. The corresponding N-protected indolones undergo alkylation at C3. Key words Key wordsγ-lactone-fused heterocycles - furoindolones - regioselectivity - carbanions Full Text References References 1a Karmakar R. Pahari P. Mal D. Chem. Rev. 2014; 114: 6213 1b Beck JJ. Chou S.-C. J. Nat. Prod. 2007; 70: 891 2a Yoganathan K. Rossant C. Ng S. Huang Y. Butler MS. Buss AD. J. Nat. Prod. 2003; 66: 1116 2b Zhou J. Gupta K. Yao J. Ye K. Panda D. Giannakakaou P. Joshi HC. J. Biol. Chem. 2002; 277: 39777 2c Shode FO. Mahomed AS. Rogers CB. Phytochemistry 2002; 61: 955 2d Holler U. Gloer JB. Wicklow DT. J. Nat. Prod. 2002; 65: 876 2e Arnone A. Assante G. Nasini G. Strada S. Vercesi A. J. Nat. Prod. 2002; 65: 48 2f Palermo JA. Rodriguez B. Maria F. Spagnuolo C. Seldes AM. J. Org. Chem. 2000; 65: 4482 2g Brady SF. Wagenaar MM. Singh MP. Janso JE. Clardy J. Org. Lett. 2000; 2: 4043 3a DeShong P. Sidler DR. J. Org. Chem. 1985; 50: 2309 3b Vegh D. Morel J. Decroix B. Zalupsky P. Synth. Commun. 1992; 22: 2057 3c Acerbi A. Carfagna C. Costa M. Mancuso R. Gabriele B. Della CaN. Chem. Eur. J. 2018; 24: 4835 4a Mal D. Senapati BK. Pahari P. Tetrahedron 2007; 63: 3768 4b Jana A. Mal D. Chem. Commun. 2010; 46: 4411 4c Roy J. Mal D. Eur. J. Org. Chem. 2014; 1873 5 Gelin S. Pollet P. J. Heterocycl. Chem. 1979; 16: 505 6 The reaction of 7 with 8 was carried out with the aim of increasing the yield of Fischer indole product 6, but interestingly pyrazole 9a′ was also obtained. For further structure confirmation, pyrazole 9a′ was oxidized to aldehyde 9b′. Pyrazole 9a′ was obtained in 55% yield when furanone 9 was treated with PTSA in refluxing ethanol (see experimental section). 7 The structure of compound 10 was further confirmed by synthesis of the N-acetyl-protected compound 10a′ and the N,N-dimethyl derivative 10b′ (see experimental section). 8 The structure of compound 12 was further confirmed by oxidation of its primary alcohol to give aldehyde derivative 12a′ (see experimental section). 9 Momose T. Toyooka N. Nishi T. Takeuchi Y. Heterocycles 1988; 27: 1907 10a Wurtz S. Rakshit S. Neumann JJ. Droge T. Florius F. Angew. Chem. Int. Ed. 2008; 47: 7230 10b He Z. Li H. Li Z. J. Org. Chem. 2010; 75: 4636 11 Several reagents were examined for the oxidative cyclization of 14; however, the desired cyclized product, furoindolone 6, was not furnished: either starting material (SM) was recovered or an intractable reaction mixture (IRM) was obtained. We tried the following combinations: Cu(OAc)2·H2O/Pd(OAc)2, K2CO3, DMF, 80 °C (SM recovered); PdCl2(PPh3)2, TEA, DMF, 110 °C (SM recovered); I2, K2CO3, DMF, 100 °C (SM recovered); Ag2O/Pd(OAc)2, KOAc, DMF, 140 °C (IRM); PPh3/Pd2(dba)3/ Cu(OAc)2·H2O, TEA, DMF, 140 °C (IRM); I2, K2CO3, DMF, 100–140 °C (IRM). 12 We tried the dehydrohalogenative cyclization of 15 with the following combinations: Cu(OAc)2, Cs2CO3, DMF, 125 °C; TBAB/Pd(OAc)2, K2CO3, DMF, 100 °C; CuI, Cs2CO3, DMF, 125 °C; PdCl2(PPh3)2, Cs2CO3, 1,4-dioxane, 100 °C; Pd(PPh3)4, TEA, DMF, 140 °C; PPh3/Pd2(dba)3, K3PO4, toluene, 120 °C; AcOH/Pd(OAc)2, 140 °C; LiCl/Pd(PPh3)4, Na2CO3, MeCN, 140 °C; LiCl, PPh3/Pd(OAc)2, K2CO3, DMF, 140 °C; PdCl2(PPh3)2, TEA, DMF, 110 °C. 13 Cunha S. Oliveira CC. Sabino JR. J. Braz. Chem. Soc. 2011; 22: 598 14a Nguyen HH. Kurth MJ. Org. Lett. 2013; 15: 362 14b Ramkumar N. Nagarajan R. J. Org. Chem. 2013; 78: 2802 14c Bernal P. Tamariz J. Helv. Chim. Acta 2007; 90: 1449 15a Chen C. Lieberman DR. Larsen RD. Verhoeven TR. Reider PJ. J. Org. Chem. 1997; 62: 2676 15b Sorensen US. Pombo-Villar E. Helv. Chim. Acta 2004; 87: 82 16 Iida H. Yuasa Y. Kibayashi C. J. Org. Chem. 1980; 45: 2938 17a Ishida T. Kikuchi S. Tsubo T. Yamada T. Org. Lett. 2013; 15: 848 17b Roman DS. Takahashi Y. Charette AB. Org. Lett. 2011; 13: 3242 18 Mal D. Anionic Annulations in Organic Synthesis. 2019. Elsevier; Supplementary Material Supplementary Material Supporting Information
