Palladium(II) Acetate−Tris(triphenylphosphine)rhodium(I) Chloride:  A Novel Catalytic Couple for the Intramolecular Heck Reaction

Abstract

A series of crotyl ethers underwent intramolecular cyclizations in the presence of a novel catalytic couple, composed of tris(triphenylphosphine)rhodium(I) chloride and palladium(II) acetate, under Heck conditions initially described by Jeffery.(1) The data indicated that the combination of these two metal catalysts formed a synergistic interaction that mediated intramolecular couplings in a superior manner as compared to the use of palladium(II) acetate alone. When tris(triphenylphosphine)rhodium(I) chloride was added to the system, a distinct increase in rate and selectivity for the endocyclic form of the bicyclic ether products was generally observed. In addition, changing parameters such as dilution and intial pot temperature appeared to significantly affect rate and selectivity in the experiments involving the catalytic couple, but not as drastically with those that were done only in the presence of palladium(II) acetate. Substitution of bis(triphenylphosphine)palladium(II) acetate for palladium(II) acetate provided an outcome that slightly favored the endocyclic form of the bicyclic ether, but when tris(triphenylphosphine)rhodium(I) chloride was added as a cocatalyst, the ratio clearly favored the exocyclic isomer.

Generation of Polar Semi‐Saturated Bicyclic Pyrazoles for Fragment‐Based Drug‐Discovery Campaigns.

“…[30] Scheme5.Synthesis of an hydroxy piperidine bicyclic derivative. However,c ontrol of the chemistry could deliver useful intermediates for further functionalisation of the tetrahydropyridine and tetrahydropyrane ring of 12 c and 14,respectively.…”

Heck Reactions with Very Low Ligandless Catalyst Loads Accelerated by Microwaves or Simultaneous Microwaves/Ultrasound Irradiation

“…[38] Except for entries 1-8 where the base was TEA, for all the other reactions we used K 2 CO 3 in the presence of TBAB. Results are summarized in Table 1.…”

Synthesis of fused indoles by sequential palladium-catalyzed Heck reaction and N-heteroannulation

“…Exclusive or highly selective formation of the exo isomer has been reported in related systems. 15,16 A vinyl-substituted cyclization product was exclusively obtained in one case (entry 3). This result can be explained mechanistically via insertion of the alkene into the oxidative addition intermediate 44 to give a new s-palladium complex 45 having a cis-relationship between the palladium moiety and the newly formed carbon-carbon bond.…”

“…benzene(15). Reaction of sodium hydride (158 mg, 6.56 mmol) with 2-(2-propen-1-yl)phenol in THF (25 mL, 1H) followed by reaction of the formed alkoxide with 7 (1.02 g, 3.44 mmol) and tetrabutylammonium iodide (127 mg, 0.35 mmol) in THF (25 mL, 42.5 h), as described for 11, gave after work up and chromatography (hexanes/EtOAc, 49:1) 15 (1.09 g, 3.14 mmol, 91%) as a faint yellow oil.1 H NMR (270 MHz) d 7.78 (d, JZ7.7 Hz, 1H), 7.64 (dd, JZ7.9, 1.2 Hz, 1H), 7.45 (t, JZ7.9 Hz, 1H), 7.20-7.15 (m, 2H), 6.94 (t, JZ7.5 Hz, 1H), 6.85 (d, JZ 8.3 Hz, 1H), 6.03 (ddq, JZ17.6, 9.5, 6.5 Hz, 1H), 5.14 (s, 2H), 5.11-5.04 (m, 2H), 3.49 (d, JZ6.5 Hz, 2H); 13 C NMR (67.5 MHz) d 155.…”