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This reaction was the first example of a carbon-carbon bond-forming reaction that followed a Pd(0)/Pd(II) catalytic cycle, the same catalytic cycle that is seen in other Pd(0)-catalyzed cross-coupling reactions. The Heck reaction is a way to substitute alkenes. [2] [3] [4] [5]
The Heck reaction is the palladium-catalyzed coupling of an aryl or alkenyl halide with an alkene to form a substituted alkene. [2] Intramolecular variants of the reaction may be used to generate cyclic products containing endo or exo double bonds. Ring sizes produced by the intramolecular Heck reaction range from four to twenty-seven atoms.
The most common type of coupling reaction is the cross coupling reaction. [1] [2] [3] Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium-catalyzed cross coupling reactions. [4] [5] Broadly speaking, two types of coupling reactions are recognized:
1972 - The Heck reaction is a coupling reaction of a halogenide with an olefin. Pd(0) intermediates are implicated. 1973 - The Trost asymmetric allylic alkylation is a nucleophilic substitution. 1975 - The Sonogashira coupling is a coupling reaction of terminal alkynes with aryl or vinyl halides.
Cross-couplings are a subset of the more general coupling reactions. Often cross-coupling reactions require metal catalysts. One important reaction type is this: R−M + R'−X → R−R' + MX (R, R' = organic fragments, usually aryl; M = main group center such as Li or MgX; X = halide) These reactions are used to form carbon–carbon bonds but ...
A 2021 survey of heterogeneous metal catalyzed cross-couplings in the fine chemical industry reported, out of 22 examples, 19 Suzuki or Heck reactions, which included only 2 examples with N-basic heterocycles, and only 4 examples with a singly-ortho-substituted electrophile (representative example in Scheme 1). [1]
The first example of a palladium catalyzed coupling of aryl halides with organotin reagents was reported by Colin Eaborn in 1976. [16] This reaction yielded from 7% to 53% of diaryl product. This process was expanded to the coupling of acyl chlorides with alkyl-tin reagents in 1977 by Toshihiko Migita, yielding 53% to 87% ketone product.
The common reagent for the coupling reaction is NHS-ester (shown in the first reaction below in Figure 1), which reacts with nucleophilic lysine through a lysine acylation mechanism. Other similar reagents are isocyanates and isothiocyanates that undergo a similar mechanism (shown in the second and third reactions in Figure 1 below). [1]