Selective Synthesis of Polysubstituted Dihydroquinolines and α,β-Unsaturated Amidines by a Catalytic Reaction of Ynamides with Ketimines

Abstract

Ynamides reacted with benzophenone imines in the presence of triflic imide as a catalyst. Ynamides bearing a sulfonamide moiety gave the corresponding 2-amino-3,4-dihydroquinolines selectively in good to high yields. In contrast, yne-carbamates gave the corresponding α,β-unsaturated amidines exclusively. These methods permit simple preparation of sterically crowded polysubstituted quinolines and α,β-unsaturated amidines.

Key words

quinolines - domino reactions - imines - amidines - amides - alkynes - cyclizations

• References

• 1a Ward SA, Bray PG, Mungthin M, Hawley SR. Ann. Trop. Med. Parasitol. 1995; 89: 121
• 1b Musiol R, Jampilek J, Kralova K, Richardson DR, Kalinowski D, Podeszwa B, Finster J, Niedbala H, Palka A, Polanski J. Bioorg. Med. Chem. 2007; 15: 1280
• 1c Michael JP. Nat. Prod. Rep. 2007; 24: 223
• 2a Katritzky AR, Rachwal S, Rachwal B. Tetrahedron 1996; 52: 15031
• 2b Kouznetsov VV, Méndez LV, Gómez CM. M. Curr. Org. Chem. 2005; 9: 141
• 2c Zhang X, Campo MA, Larock RC. Org. Lett. 2005; 7: 763
• 2d Luo Y, Li Z, Li C.-J. Org. Lett. 2005; 7: 2675
• 2e Gabriele B, Mancuso R, Salerno G, Ruffolo G, Plastina P. J. Org. Chem. 2007; 72: 6873
• 2f Huo Z, Gridnev ID, Yamamoto Y. J. Org. Chem. 2010; 75: 1266
• 2g Shindoh H, Tokuyama H, Takemoto Y. J. Org. Chem. 2008; 73: 7451
• 2h Tsuritani T, Yamamoto Y, Kawasaki M, Mase T. Org. Lett. 2009; 11: 1043
• 3a Evano G, Coste A, Jouvin K. Angew. Chem. Int. Ed. 2010; 49: 2840
• 3b DeKorver KA, Li H, Lohse AG, Hayashi R, Lu Z, Zhang Y, Hsung RP. Chem. Rev. 2010; 110: 5064
• 4a Shindoh N, Takemoto Y, Takasu K. Chem. Eur. J. 2009; 15: 7026
• 4b Shindoh N, Kitaura K, Takemoto Y, Takasu K. J. Am. Chem. Soc. 2011; 133: 8470
• 5 Takasu K. Synlett 2009; 1905
• 6 Shindoh N, Takemoto Y, Takasu K. Heterocycles 2011; 82: 1133
• 7 Crystallographic data for compounds 3ca and 4ch have been deposited with the accession numbers CCDC 945444 and 945445, respectively, and can be obtained free of charge from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK, Fax: [phone], E-mail: [e-mail], Web site: www.ccdc.cam.ac.uk/conts/retrieving.html.
• 8 No reaction occurred in the presence of the following Lewis acids: Ce(OTf)₃, Yb(OTf)₃, In(OTf)₃, Y(OTf)₃, AgOTf, Sc(OTf)₃, Zn(OTf)₂, Fe(OTf)₃, and PtCl₄ .

For selected recent reviews, see:
• 9a Caddick S, Fitzmaurice R. Tetrahedron 2009; 65: 3325
• 9b Kappe CO, Dallinger D. Mol. Diversity 2009; 13: 71
• 9c Kappe CO. Chem. Soc. Rev. 2008; 37: 1127
• 9d Jindal R, Bajaj S. Curr. Org. Chem. 2008; 12: 836
• 9e Solinas A, Taddei M. Synthesis 2007; 2409
• 10 A DFT study (B3LYP/6-31G^*) indicated that the ground-state energy difference (ΔG ^o) between the two diastereomers of 4ja was 4.32 kJ/mol (Boltzmann distribution 86:15). The calculated value is reasonably consistent with the experimental one (77:23).

For Diels–Alder reactions of azoquinone methides, see:
• 11a Hodgett I, Noyce SJ, Storr RC. Tetrahedron Lett. 1984; 25: 5435
• 11b Wu H, Xiao X, Qin Y. Synlett 2011; 907
• 12 Sagamanova IK, Kurts KC. M, Hsung RP. Org. Synth., Coll. Vol. XI . John Wiley & Sons; London: 2009: 677
• 13 Larsen SB, Andersen BB, Johansen TN, Jørgensen M. Tetrahedron 2008; 64: 2938