Preparation of Silica-HClO₄ catalyst: Perchloric acid (1.25 g, as a 70% aqueous solution) was added to the suspension of silica gel (23.75 g, mesh 230–400) in Et₂O. The mixture was concentrated and the residue was heated at 100 °C for 72 h under vacuum to afford Silica-HClO₄ as a free flowing powder. http://dx.doi.org/10.1039/B304178F

Procedure for synthesis of titled product: To the solution of ortho-cresol (300 mg, 1 mmol) in acetonitrile (25 mL) were added formaldehyde (0.25 mL, 3 mmol), caprolactam (471 mg, 1.5 mmol) and 50% w/w silica-HClO₄ (150 mg). The mixture was then heated to reflux at 80 °C for 6 h. Completion of the reaction was monitored by TLC (by observing the disappearance of ortho-cresol on TLC). Reaction mixture was then cooled to room temperature and filtered through filter paper. The filtrate was concentrated on  a rotary evaporator to give the crude product as a yellow oil. Purification by silica gel (mesh 100-200) column chromatography using EtOAc: Hexane - 1:1 as eluent gave product as white solid (84% yield).

• Reaction proceeds through o-quinone methide (o-QM) and an oxazine intermediate via tandem Knoevenagel condensation, formal [4+2]-Diels-Alder cycloaddition and acid catalyzed oxazine ring opening
• The titled product can also be obtained using N-vinyl caprolactam instead of caprolactam under similar reaction conditions. In the presence of Silica-HClO₄ catalyst, N-vinyl caprolactam undergoes devinylation to produce caprolactam which then participates in amidoalkylation reaction
• The protocol is applicable to structurally diverse phenols

1-(2-Hydroxy-3-methyl benzyl)azepan-2-one: White solid; m.p. 141-143 °C

¹H NMR (CDCl₃, 400 MHz): d ppm 9.63 (s, 1H), 7.10 (d, J = 7.6 Hz, 1H), 6.96 (d, J = 6.4 Hz, 1H), 6.71 (t, J = 7.6 Hz, 1H), 4.42 (s, 2H), 3.44 (t, J = 4.8 Hz, 2H), 2.57 (d, J = 6.0 Hz, 2H), 2.28 (s, 3H), 1.74-1.71 (m, 4H), 1.69-1.63 (m, 2H)

¹³C NMR (CDCl₃, 100 MHz): d ppm 178.1, 154.5, 131.4, 128.6, 126.5, 121.9, 118.8, 50.0, 49.7, 36.6, 29.9, 27.6, 23.2, 16.6

IR (CHCl₃) 3089, 2929, 2855, 1609, 1590, 1496, 1445, 1354, 1261, 1229, 1197, 1174, 1085, 1019 cm^-1

ESI-MS m/z 234.1 [M+1]⁺

Mudududdla, R.; Jain, S.K.; Bharate, J.B.; Gupta, A.P.; Singh, B.; Vishwakarma, R.A.; Bharate, S.B. Ortho-Amidoalkylation of phenols via tandem one-pot approach involving oxazine intermediate. J. Org. Chem. 2012, 77, 8821-8827 http://dx.doi.org/10.1021/jo3017132

Wang, B.-L.; Li, N.-K.; Zhang, J.-X.; Liu, G.-G.; Liu, T.; Shen, Q.; Wang, X.-W. Org. Biomol. Chem. 2011, 9, 2614–2617. http://dx.doi.org/10.1039/C0OB01200A.

Barry, J. E.; Mayeda, E. A.; Ross, S. D. Tetrahedron 1977, 33, 369-372. http://dx.doi.org/10.1016/0040-4020(77)80088-4