Palladium-Catalyzed [1,3]-O-to-N Rearrangement of Allylic ­Imidates

Abstract

The rearrangement of allylic imidates is a powerful transformation for the synthesis of allylic amines. Whereas the [3,3]-rearrangement has long been established as the Overman rearrangement, the corresponding [1,3]-rearrangement is rare. Here, we report a novel strategy for the [1,3]-rearrangement of imidates based on the oxidative addition of a palladium(0) catalyst to an allylic imidate. Structurally distinct allylic amides could be synthesized under mild and base-free conditions.

Key words

palladium catalysis - allylic substitution - [1,3]-rearrangement - imidates - amides

• References and Notes

• 1a Nag S, Batra S. Tetrahedron 2011; 67: 8959
• 1b Trost BM, Crawley ML. Chem. Rev. 2003; 103: 2921
• 2a Ramirez TA, Zhao B, Shi Y. Chem. Soc. Rev. 2012; 41: 931
• 2b Guillena G, Ramón DJ, Yus M. Chem. Rev. 2010; 110: 1611
• 2c Johannsen M, Jørgensen KA. Chem. Rev. 1998; 98: 1689
• 2d Cheikh RB, Chaabouni R, Laurent A, Mison P, Nafti A. Synthesis 1983; 685

For seminal references, see:
• 3a Overman LE. J. Am. Chem. Soc. 1974; 96: 597
• 3b Overman LE. J. Am. Chem. Soc. 1976; 98: 2901

For selected reviews on the Overman rearrangement, see:
• 4a Overman LE. Acc. Chem. Res. 1980; 13: 218
• 4b Fernandes RA, Kattanguru P, Gholap SP, Chaudhari DA. Org. Biomol. Chem. 2017; 15: 2672

O-to-N alkyl migratory rearrangements of β-hydroxy α-diazo carbonyl compounds have been reported, see:
• 5a Shi W, Jiang N, Zhang S, Wu W, Du D, Wang J. Org. Lett. 2003; 5: 2243
• 5b Zhang Z, Shi W, Zhang J, Zhang B, Liu B, Liu Y, Fan B, Xiao F, Xu F, Wang J. Chem. Asian J. 2010; 5: 1112
• 5c Trost BM, Malhotra S, Ellerbrock P. Org. Lett. 2013; 15: 440
• 6a Hoffmann MG, Schmidt RR. Liebigs Ann. Chem. 1985; 2403
• 6b Li C, Wang J. J. Org. Chem. 2007; 72: 7431
• 6c Adhikari AA, Suzuki T, Gilbert RT, Linaburg MR, Chisholm JD. J. Org. Chem. 2017; 82: 3982

For seminal examples of acid-catalyzed [1,3]-rearrangement of imidates, see:
• 7a Cramer F, Pawelzik K, Kupper J. Angew. Chem. 1956; 68: 649
• 7b Cramer F, Hennrich N. Chem. Ber. 1961; 94: 976
• 8 For a review of [1,3]-rearrangement of glycosyl trichloroacetimidates, see: Christensen HM, Oscarson S, Jensen HH. Carbohydr. Res. 2015; 408: 51
• 9a Galeazzi R, Martelli G, Orena M, Rinaldi S. Synthesis 2004; 2560
• 9b Galeazzi R, Martelli G, Orena M, Rinaldi S, Sabatino P. Tetrahedron 2005; 61: 5465
• 9c Kobbelgaard S, Brandes S, Jørgensen KA. Chem. Eur. J. 2008; 14: 1464
• 10 Arnold JS, Zhang Q, Nguyen HM. Eur. J. Org. Chem. 2014; 4925

For seminal references on palladium(0)-mediated allylic alkylation, see:
• 11a Tsuji J, Takahashi H, Morikawa M. Tetrahedron Lett. 1965; 6: 4387
• 11b Trost BM, Fullerton TJ. J. Am. Chem. Soc. 1973; 95: 292
• 12 For a selected review of palladium(0)-catalyzed allylic alkylation, see: Trost BM, Van Vranken DL. Chem. Rev. 1996; 96: 395
• 13 Fristrup P, Jensen T, Hoppe J, Norrby P.-O. Chem. Eur. J. 2006; 12: 5352
• 14a Yamada Y, Mukai K, Yoshioka H, Tamaru Y, Yoshida Z.-i. Tetrahedron Lett. 1979; 20: 5015
• 14b Tamaru Y, Yoshida Z, Yamada Y, Mukai K, Yoshioka H. J. Org. Chem. 1983; 48: 1293
• 14c Hiroi K, Kitayama R, Sato S. J. Chem. Soc., Chem. Commun. 1984; 303
• 14d Auburn PR, Whelan J, Bosnich B. Organometallics 1986; 5: 1533
• 14e Hiroi K, Makino K. Chem. Pharm. Bull. 1988; 36: 1744
• 14f Harayama H, Nagahama T, Kozera T, Kimura M, Fugami K, Tanaka S, Tamaru Y. Bull. Chem. Soc. Jpn. 1997; 70: 445
• 14g Böhme A, Gais H.-J. Tetrahedron: Asymmetry 1999; 10: 2511
• 14h Gais H.-J, Böhme A. J. Org. Chem. 2002; 67: 1153
• 14i Jagusch T, Gais H.-J, Bondarev O. J. Org. Chem. 2004; 69: 2731
• 15a Yeung CS, Hsieh TH. H, Dong VM. Chem. Sci. 2011; 2: 544
• 15b Pan S, Ryu N, Shibata T. Org. Lett. 2013; 15: 1902
• 16 2,2,2-Trichloro-N-[(2E)-3-cyclohexylprop-2-en-1-yl]acetamide (2b); Typical Procedure In an argon-filled glove box, Pd₂(dba)₃ (9.2 mg, 0.010 mmol) and L1 (40.0 mg, 0.100 mmol) were weighed into a 4 mL vial equipped with a stirrer bar. CH₂Cl₂ (1.0 mL) was added, and the resulting mixture was stirred at RT for 5 min while the color of the mixture changed from dark wine-red to green-amber. The solution of the palladium complex was transferred to a separate 4 mL vial containing imidate 1b (113 mg, 0.400 mmol), and the vessel was sealed with a Teflon-lined cap. The mixture was stirred at RT for 21 h then directly passed through a silica gel plug that was washed thoroughly with CH₂Cl₂. The solvent was removed from the filtrate, and the residue was purified by column chromatography [silica gel, hexanes–EtOAc (100:0 to 90:10)] to give a white solid; yield: 100 mg (88%; E/Z = 97:3); mp 69–71 °C; R_f = 0.40 (hexanes–EtOAc, 5:1; UV). ¹H NMR (400 MHz, CDCl₃): δ = 6.66 (br s, 1 H), 5.67 (dd, J = 15.4, 6.6 Hz, 1 H), 5.43 (dt, J = 15.4, 6.1 Hz, 1 H), 3.92 (d, J = 6.1 Hz, 2 H), 2.01−1.94 (m, 1 H), 1.73−1.64 (m, 5 H), 1.32−1.02 (m, 5 H). ¹³C NMR (100 MHz, CDCl₃): δ = 161.5, 141.1, 121.1, 92.6, 43.3, 40.2, 32.5, 26.0, 25.8. HRMS (ESI): m/z [M + Na]⁺ calcd for C₁₁H₁₆Cl₃NNaO: 306.0190; found: 306.0184.
• 17 Moreno-Mañas M, Morral L, Pleixats R. J. Org. Chem. 1998; 63: 6160 ; and references therein
• 18 Hayashi T, Hagihara T, Konishi M, Kumada M. J. Am. Chem. Soc. 1983; 105: 7767