Palladium-Catalyzed Reaction of Aryl Iodides with ortho- Bromoanilines and Norbornene/Norbornadiene: Unexpected Formation of Dibenzoazepine Derivatives-

Reaction Scheme


The cross-coupling reaction of aryl bromides and iodides with aliphatic and aromatic thiols catalyzed by palladium complexes of the bisphosphine ligand CyPF-tBu (1) is reported. Reactions occur in excellent yields, broad scope, high tolerance of functional groups, and with turnover numbers that exceed those of previous catalysts by 2 or 3 orders of magnitude. These couplings of bromo- and iodoarenes are more efficient than the corresponding reactions of chloroarenes and could be conducted with less catalyst loading and/or milder reaction conditions. Consequently, limitations regarding scope and functional group tolerance previously reported in the coupling of aryl chlorides are now overcome.



Preparation of Stock Solution A (1.0 x 10-2 M). DME (1.0 mL) was added to a mixture of Pd(OAc)2 (2.2 mg) and CyPF-tBu (5.5 mg). The resulting orange solution was stirred at room temperature for 1 min before being used. Preparation of Stock Solution B (1.0 x 10-4 M). Ten microliters of stock solution A was diluted to 1.0 mL with DME. The resulting pale yellow solution was stirred at room temperature for 1 min before being used. General Procedure for the Coupling of Aryl Bromides and Iodides with Aliphatic and Aromatic Thiols. The appropriate quantity of stock solution A or B was added to a 4 mL vial containing the aryl bromide or iodide (1.00 mmol) and NaOtBu (106 mg, 1.10 mmol) in DME (1.5 mL). The thiol (1.00 mmol) was then added and the vial sealed with a cap containing a PTFE septum. The mixture was heated at the temperature indicated in Tables 4 and 5 until the aryl halide was consumed, as determined by GC. Silica gel (0.5 g) was added, and the solvents were evaporated under reduced pressure. The crude residue was purified by column chromatography on silica gel with hexane or a mixture of hexane and ethyl acetate as eluent. Aryl sulfides were isolated in the yields reported in Tables 4 and 5.



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