PPh₃AuTFA Catalyzed in the Dearomatization of 2-Naphthols with Allenamides

Abstract

General Methods.1 H-NMR spectra were recorded on Varian 400 (400 MHz) spectrometers. Chemical shifts are reported in ppm from TMS with the solvent resonance as the internal standard (deuterochloroform: 7.24 ppm). Data are reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, sext = sextet, sept = septet, p = pseudo, b = broad, m = multiplet), coupling constants (Hz). 13 C-NMR spectra were recorded on a Varian 400 (100 MHz) spectrometers with complete proton decoupling. Chemical shifts are reported in ppm from TMS with the solvent as the internal standard (deuterochloroform: 77.0 ppm). Monodimensional NOE experiment (400 MHz, CDCl 3 , 25 °C) was performed by using a DPFGSE-NOE sequence, with a 50 Hz pulse and a mixing time of 1.5 s. Irradiation at the frequency of proton H 1 (5.65 ppm) showed strong positive NOE response of the H 4 frequency, confirming the sin-relationship. Weaker NOE effects were also observed for the equatorial H 2 and the axial H 3 protons. GC-MS spectra were taken by EI ionization at 70 eV on a Hewlett-Packard 5971 with GC injection. They are reported as: m/z (rel. intense). LC-electrospray ionization mass spectra were obtained with Agilent Technologies MSD1100 single-quadrupole mass spectrometer. Chromatographic purification was done with 240-400 mesh silica gel. Other anhydrous solvents were supplied by Sigma Aldrich in Sureseal® bottles and used without any further purification. Commercially available chemicals were purchased from Sigma Aldrich, Stream and TCI and used without any further purification. Melting points were determined with Bibby Stuart Scientific Melting Point Apparatus SMP 3 and are not corrected. Agilent Technologies LC/MSD Trap 1100 series (nebulizer: 15.0 PSI, dry Gas: 5.0 L/min, dry Temperature: 325 °C, capillary voltage positive scan: 4000 mA, capillary voltage negative scan: 3500 mA). Preparation of β-naphthols 1 [1] and N-allenyl amides [2] were accomplished following the reported procedures.

A complementary approach to conjugated N-acyliminium formation through photoredox-catalyzed intermolecular radical addition to allenamides and allencarbamates

“…Importantly, this unique reactivity has underpinned allenamide chemistry and led to the development of a number of innovative transformations, including cycloadditions [5][6][7][8][9], intramolec-ular cyclizations and intermolecular addition reactions [10][11][12][13][14][15][16][17][18], as well as the use of the allenamide building block in natural product synthesis [1].…”

“…Addition reactions of allenamides, which can also encompass intramolecular cyclizations, are typically promoted by the electrophilic activation of the β-carbon of the allenamide. This can be achieved using various electrophilic methods, including the use of Brönsted acids [15,[19][20][21][22], halogenation sources [16,18,[23][24][25][26][27][28], by means of oxidation [20,[29][30][31] or through the use of a transition metal such as Au(I) [8,[10][11][12][13][14][15][16][32][33][34][35][36]. The reaction of the allenamide with an electrophilic source promotes the formation of a conjugated N-acyliminium intermediate 2 [ [37][38][39][40] that subsequently undergoes an addition reaction with a suitable nucleophile (Scheme 1).…”

New Chiral BINOL‐Based Phosphates for Enantioselective [Au(I)]‐Catalyzed Dearomatization of β‐Naphthols with Allenamides

“…In conjunction with our ongoing interests towards the implementation of catalytic dearomative protocols, [7,8] we recently documented the use of achiral cationic [Au(I)] complexes for the intra‐ [9a] as well as intermolecular [9b] dearomatization of 2‐naphthols by means of terminal/internal alkynes and allenamides. The latter approach highlights the crucial role of the counterion in homogenous gold catalysis, which is frequently underestimated during the reaction condition optimization [10] .…”

Recent Advances in the Catalytic Dearomatization of Naphthols

“…Analogously, the intermolecular condensation of allenamides with β‐naphthols was also documented by us in the presence of LAuTFA catalysts. In this case, the use of trifluoroacetate as a counterion was crucial in order to achieve the C(1)‐alkylation in high yields , …”