Zirconocene-Initiated Intramolecular Hydride Transfer in N-Iso­alkyl-Substituted Propargylamines

Abstract

The unusual transformation of N-isoalkyl-substituted propargylamines into alkenylamines under the action of Cp₂ZrCl₂ and organoaluminum compounds (Me₃Al, EtAlCl₂) has been observed. The proposed mechanism, involving the N-isoalkyl-substituted propargylamine undergoing zirconocene-initiated intramolecular hydride transfer was supported by B3LYP/6-31G(d)/LanL2DZ calculations.

Key words

alkenylamine - hydride transfer - negative hyperconjugation - propargylamine - zirconocene cation

• References and Notes

• 1 Negishi E.-i. ARKIVOC 2011; (viii): 34
• 2 Dzhemilev UM. D’yakonov VA. Modern Organoaluminum Reagents, in Topics in Organometallic Chemistry . Vol. 41; Woodward S. Dagorne S. Springer; Berlin, Heidelberg: 2013: 215
• 3 Negishi E. Bull. Chem. Soc. Jpn. 2007; 80: 233
• 4 Ramazanov IR. Kadikova RN. Dzhemilev UM. Russ. Chem. Bull. 2011; 60: 99
• 5 Wang G. Zhu G. Negishi E.-i. J. Organomet. Chem. 2007; 692: 4731
• 6 Rand CL. Van Horn DE. Moore MW. Negishi E. J. Org. Chem. 1981; 46: 4093
• 7 Khanna A. Maung C. Johnson KR. Luong TT. Van Vranken DL. Org. Lett. 2012; 14: 3233
• 8 Giannini U. Brückner G. Pellino E. Cassata A. J. Polym. Sci., Part C 1968; 22: 157
• 9 Giannini U. Brückner G. Pellino E. Cassata A. J. Polym. Sci., Part B : Polym. Lett. 1967; 5: 527
• 10 Chung TC. In Functionalization of Polyolefins . Academic Press; San Diego: 2002: 39
• 11 Bochmann M. J. Chem. Soc., Dalton Trans. 1996; 255
• 12 Yoshida T. Negishi E. J. Am. Chem. Soc. 1981; 103: 4985
• 13 Wipf P. Lim S. Angew. Chem., Int. Ed. Engl. 1993; 32: 1068
• 14 Negishi E. Van Horn DE. Yoshida T. J. Am. Chem. Soc. 1985; 107: 6639
• 15 (E)-2-d-N-Isopropyloct-2-en-1-amine (1a)To a 25 mL, argon-swept flask, equipped with a magnetic stirrer and rubber septum, was added Cp₂ZrCl₂ (585 mg, 2 mmol) suspended in CH₂Cl₂ (5 mL) and Me₃Al (0.38 mL, 4 mmol; caution: organoaluminums are pyrophoric and can ignite on contact with air, water or any oxidizer!) at room temperature. To the solution was added N,N-diisopropyloct-2-yn-1-amine (418 mg, 2 mmol) at room temperature and stirred for 3 h at 40 °C. Then, the reaction mixture was diluted with with hexane (5 mL), and D₂O (3 mL) was added dropwise while cooling the reactor flask in an ice bath. The precipitate was filtered on a filter paper. The aqueous layer was extracted with diethyl ether (3 × 5 mL). The combined organic layers were washed with brine (10 mL), dried over anhydrous CaCl₂. Evaporation of solvent and purification of the residue by column chromatography (hexane/ethyl acetate, 5:1) gave a colourless oil; yield 279 mg (82%); R_f = 0.8 (hexane/ethyl acetate, 5:1). ¹H NMR (400 MHz, CDCl₃): δ = 0.85 (t, J = 6.9 Hz, 3 Н, С(11)Н₃), 1.02 (d, J = 6.3 Hz, 6 Н, С(5,6)Н₃), 1.17–1.30 (m, 4 Н, С(9,10)Н₂), 1.30–1.37 (m, 2 Н, С(8)Н₂), 1.98 (q, J = 7.1 Hz, 2 Н, С(7)Н₂), 2.74–2.83 (m, 1 Н, С(4)Н₁), 3.14 (s, 2 Н, С(1)Н₂), 5.45–5.60 (m, 1 Н, С(3)Н₁). ¹³C NMR (100 MHz, CDCl₃): δ = 13.97 (C(11)), 22.47 and 31.35 (C(9) and C(10)), 22.88 (2 C, С(5,6)), 28.93 (C(8)), 32.25 (С(7)), 47.99 (С(4)), 49.30 (C(1)), 128.08 (t, ¹ J _CD =18.5 Hz, C(2)), 132.34 (С(3)). MS (EI): m/z (%) = 170 (4) [М]⁺, 155 (22), 141 (<1), 127 (2), 111 (8), 99 (12), 82 (7), 69 (31), 44 (100), 41 (21). Anal. Calcd (%) for C₁₁H₂₂DN: C, 77.57; N, 8.22. Found: C, 77.7; N, 8.3.
• 16 Papirer E. In Surfactant Science Series . Vol. 90. Marcel Dekker; New York: 2000: 690
• 17 Meerwein H. Allendörfer H. Beekmann P. Kunert F. Morschel H. Pawellek F. Wunderlich K. Angew. Chem. 1958; 70: 211
• 18 Kaitmazova GS. Gambaryan NP. Rokhlin EM. Russ. Chem. Rev. 1989; 58: 1145