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DOI: 10.1055/s-2003-39881
Saturated N-Heterocyclic Carbene Oxime and Amine Palladacycle Catalysis of the Mizoroki-Heck and the Suzuki Reactions [1]
Publication History
Publication Date:
11 June 2003 (online)
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Abstract
ortho-Palladated aryl oxime and amines with a N-heterocyclic carbene ligand show increased thermal stability and catalyze the Mizoroki-Heck and Suzuki reaction with high yields, and moderate TON (2,000-92,000) and TOF (200-4,300 h-1). Homo coupling of the aryl halides gave low yields of the biaryls in the presence of these catalysts.
Key words
saturated N-heterocyclic carbene - oxime and amine palladacycle - Mizoroki-Heck reaction - Suzuki reaction - biaryl
NCL Communication No.: 6643
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References
NCL Communication No.: 6643
7Iyer, S.; Jayanthi, A.; Kulkarni, G. M.; Subramanyam, S.; Kashinath, D. K., unpublished results from our research group.
10All compounds reported are known and
were characterized by spectroscopic methods
(a) Mizoroki-Heck
reaction with benzophenone oxime carbene palladacycle (Cat 3) : To 5.175 g (25 mmol) of 1-bromonaphthalene,
styrene (3.03 g, 30 mmol) and 25 mL N-methylpyrrolidinone were added
to, followed by 2.49 g (30 mmol) of NaOAc and 0.00022 g (0.0004
mmol) of the (Cat 3) benzophenone oxime
palladacycle carbene catalyst. The reaction mixture was heated to
140-150 °C in an oil bath until the bromonaphthalene
was completely consumed (36 h). HCl (10%, 100 mL) was added
to the reaction mixture and extracted with ethyl acetate (3 × 100
mL). Washing the organic extracts with brine, drying over anhydrous
Na2SO4, concentration on a rotary evaporator
and purification by column chromatography (silica gel : 100-200
mesh) gave 5.32 g (92.6%, TON 61, 956) of E-1-naphthylstilbene.
(b)
Suzuki coupling of bromobenzene with phenyl boronic acid catalyzed
by carbene palladacycle (Cat - 2)
: Bromobenzene (0.314 g, 2 mmol), phenyl boronic acid (0.367 g,
3 mmol), catalyst (3, 0.0004 g, 0.0007
mmol) and K3PO4 (0.920 g, 4.34 mmol) were
dissolved in DMF (5 mL) and the reaction mixture heated to 120 °C
for 24 h. The biphenyl product was isolated by addition of HCl (10%,
25 mL) and extracted with ethyl acetate followed by purification
by column chromatography (silica gel : 100-200 mesh) in
73.3% (0.226 g, TON 2, 096) yield.
(c) Biaryl
coupling catalyzed by carbene palladacycle (Cat - 2) and K2CO3. 2-Bromopyridine
(0.158 g, 1.0 mmol), K2CO3 (0.165 g, 1.2 mmol),
catalyst (2, 0.0017 g, 0.003 mmol) were
dissolved in DMF (5 mL) and heated to 140 °C for 24 h.
The bipyridyl was isolated by the usual extractive procedure with
water and ethyl acetate. Purification by column chromatography (silica
gel: 100-200 mesh) gave 0.025 g (16%) yield of
the 2,2′-bipyridyl. 1H NMR (δ,
200 MHz, CDCl3) 8.69-8.71 (d, 2 H), 8.39-8.43
(d, 8 Hz, 2 H), 7.80-7.88 (m, 2 H), 7.27-7.36
(m, 2H).