Castro–Stephens coupling

Castro–Stephens coupling
Named after Charles E. Castro
Robert D. Stephens
Reaction type Coupling reaction
Identifiers
RSC ontology ID RXNO:0000525

The Castro–Stephens coupling is a cross coupling reaction between a copper(I) acetylide and an aryl halide in pyridine, forming a disubstituted alkyne and a copper(I) halide.[1][2]

General scheme for Castro-Stephens coupling

The reaction was described in 1963 by chemists Castro and Stephens.[1][2] The reaction is similar to the much older Rosenmund–von Braun synthesis (1914)[3][4] between aryl halides and copper(I) cyanide and was itself modified in 1975 as the Sonogashira coupling by adding a palladium catalyst and preparing the organocopper compound in situ, allowing copper to also be used catalytically.[5][6]

A typical reaction diphenylacetylene is obtained by the coupling of iodobenzene with CuC2C6H5 in hot pyridine:[1]

Application of Castro–Stephens coupling with phenyliodide.

Unlike the Sonogashira coupling, the Castro–Stephens coupling can produce heterocyclic compounds when a nucleophilic group is ortho to the aryl halide, although this typically requires use of dimethylformamide (DMF) as solvent.[7][8]

Application of Castro-Stephens coupling with o-iodobenzoic acid to produce an isocoumarin.

References
  1. Stephens, R. D.; Castro, C. E. (1963). "The Substitution of Aryl Iodides with Cuprous Acetylides. A Synthesis of Tolanes and Heterocyclics". J. Org. Chem. 28 (12): 3313–3315. doi:10.1021/jo01047a008.
  2. Owsley, D. C.; Castro, C. E. (1972). "Substitution of Aryl Halides with Copper(I) Acetylides: 2-Phenylfuro[3,2-b]pyridine". Organic Syntheses. 52: 128. doi:10.15227/orgsyn.052.0128.; Collective Volume, vol. 6, p. 916
  3. Rosenmund, Karl W.; Struck, Erich (1919). "Das am Ringkohlenstoff gebundene Halogen und sein Ersatz durch andere Substituenten. I. Mitteilung: Ersatz des Halogens durch die Carboxylgruppe" [The halogen bound to the ring carbon and its replacement by other substituents. I. Notice: Replacement of the halogen by the carboxyl group]. Ber. Dtsch. Chem. Ges. A/B (in German). 52 (8): 1749–1756. doi:10.1002/cber.19190520840.
  4. von Braun, Julius; Manz, Gottfried (1931). "Fluoranthen und seine Derivate. III. Mitteilung" [Fluoranthene and its derivatives. III. Notification]. Justus Liebigs Ann. Chem. (in German). 488 (1): 111–126. doi:10.1002/jlac.19314880107.
  5. Sonogashira, Kenkichi; Tohda, Yasuo; Hagihara, Nobue (1975). "A convenient synthesis of acetylenes: Catalytic substitutions of acetylenic hydrogen with bromoalkenes, iodoarenes and bromopyridines". Tetrahedron Lett. 16 (50): 4467–4470. doi:10.1016/s0040-4039(00)91094-3.
  6. Sonogashira, Kenkichi (2002). "Development of Pd-Cu catalyzed cross-coupling of terminal acetylenes with sp2-carbon halides". J. Organomet. Chem. 653 (1–2): 46–49. doi:10.1016/s0022-328x(02)01158-0.
  7. Batu, Gunes; Stevenson, Robert (1980). "Synthesis of natural isocoumarins, artemidin and 3-propylisocoumarin". J. Org. Chem. 45 (8): 1532–1534. doi:10.1021/jo01296a044.
  8. Castro, Charles E.; Havlin, R.; Honwad, V. K.; Malte, A. M.; Moje, Steve W. (1969). "Copper(I) Substitutions. Scope and Mechanism of Cuprous Acetylide Substitutions". J. Am. Chem. Soc. 91 (23): 6464–6470. doi:10.1021/ja01051a049.
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