Synthesis of Isoquinolinium-2-yl Amides via Silver(I)-Catalyzed Ring Closure of N′-(2-Alkynylbenzylidene)hydrazides

Abstract

An efficient one-pot protocol for the synthesis of isoquinolinium-2-yl amides starting from readily available hydrazides and 2-alkynylbenzaldehydes is described. The key step of the protocol is a silver(I)-catalyzed ring-closure of N′-(2-alkynylbenzylidene)hydrazides that are generated in situ. Isoquinolinium-2-yl amides derived from tert-butoxycarbonyl hydrazide could be further deprotected, delivering 2-aminoisoquinolinium trifluoroacetates.

Key words

alkynes - hydrazides - isoquinolines - annulation - ylides - silver catalysis

References

• 1a Roesch KR. Larock RC. Org. Lett.  1999,  1:  553 
• 1b Huang Q. Hunter JA. Larock RC. Org. Lett.  2001,  3:  2973 
• 1c Huang Q. Hunter JA. Larock RC. J. Org. Chem.  2002,  67:  3437 
• 1d Huang Q. Larock RC. Tetrahedron Lett.  2002,  43:  3557 
• 1e Roesch KR. Larock RC. J. Org. Chem.  2002,  67:  86 
• 1f Dai G. Larock RC. Org. Lett.  2002,  4:  193 
• 1g Dai G. Larock RC. J. Org. Chem.  2002,  67:  7042 
• 1h Dai G. Larock RC. J. Org. Chem.  2003,  68:  920 
• For a Ag(I)-promoted protocol in which indole acts as a leaving group (N-N bond cleavage), see:
• 2a Ghavtadze N. Fröhlich R. Würthwein E.-U. Eur. J. Org. Chem.  2010,  1787 
• Similarly, N₂ acts as a leaving group in the Lewis acid catalyzed or electrophile-mediated cyclization of 2-alkynyl-benzyl azides, see:
• 2b Zhang H.-P. Yu S.-C. Liang Y. Peng P. Tang B.-X. Li J.-H. Synlett  2011,  982 
• 2c Zhang H.-P. Yang X.-H. Peng P. Li J.-H. Synthesis  2011,  1219 
• 2d Niu Y.-N. Yan Z.-Y. Gao G.-L. Wang H.-L. Shu X.-Z. Ji K.-G. Liang Y.-M. J. Org. Chem.  2009,  74:  2893 
• 2e Fischer D. Tomeba H. Pahadi NK. Patil NT. Yamamoto Y. Angew. Chem. Int. Ed.  2007,  46:  4764 
• 2f Fischer D. Tomeba H. Pahadi NK. Patil NT. Huo Z. Yamamoto Y. J. Am. Chem. Soc.  2008,  130:  15720 
• 3a Ye Y. Ding Q. Wu J. Tetrahedron  2008,  64:  1378 
• 3b Ding Q. Wang B. Wu J. Tetrahedron  2007,  63:  12166 
• 3c Markina NA. Mancuso R. Neuenswander B. Lushington GH. Larock RC. ACS Comb. Sci.  2011,  13:  265 
• 4 Yeom H.-S. Kim S. Shin S. Synlett  2008,  924 
• 5a Ding Q. Wu J. Adv. Synth. Catal.  2008,  350:  1850 
• 5b Huo Z. Tomeba H. Yamamoto Y. Tetrahedron Lett.  2008,  49:  5531 
• 6 Ding Q. Chen Z. Yu X. Peng Y. Wu J. Tetrahedron Lett.  2009,  50:  340 
• For one-pot/tandem procedures involving intermediates of types 6 and 7, see:
• 7a Ding Q. Wang Z. Wu J. Tetrahedron Lett.  2009,  50:  198 
• 7b Ye S. Gao K. Wu J. Adv. Synth. Catal.  2010,  352:  1746 
• 7c Ye S. Wang H. Wu J. Eur. J. Org. Chem.  2010,  6436 
• 7d Chen Z. Yu X. Su M. Yang X. Wu J. Adv. Synth. Catal.  2009,  351:  2702 
• 7e Ding Q. Wang Z. Wu J. J. Org. Chem.  2009,  74:  921 
• For one-pot/tandem procedures involving intermediates of types 9 and 10, see:
• 8a Chen Z. Yu X. Wu J. Chem. Commun.  2010,  46:  6356 
• 8b Chen Z. Wu J. Org. Lett.  2010,  12:  4856 
• 8c Yu X. Ye S. Wu J. Adv. Synth. Catal.  2010,  352:  2050 
• 8d Ye S. Yang X. Wu J. Chem. Commun.  2010,  46:  5238 
• 8e Li S. Wu J. Org. Lett.  2011,  13:  712 
• 8f Yu X. Yang X. Wu J. Org. Biomol. Chem.  2009,  7:  4526 
• 8g Chen Z. Pan X. Wu J. Synlett  2011,  964 
• 8h Yu X. Pan X. Wu J. Tetrahedron  2011,  67:  1145 
• 9 For other related processes, see: Su S. Porco JA. J. Am. Chem. Soc.  2007,  129:  7744 
• Compounds of this type can alternatively be prepared by direct N-amination of the isoquinolines or other heterocycles, see:
• 11a Legault C. Charette AB. J. Org. Chem.  2003,  68:  7119 
• 11b Tamura Y. Matsugashita S. Ishibashi H. Ikeda M. Tetrahedron  1973,  29:  2359 
• 11c Tamura Y. Minamikawa J. Ikeda M. Synthesis  1977,  1 ; and references therein

10

So far, only the application of tosyl hydrazide (12e) was sufficiently explored in related processes; see refs. 6 and 8.