Heck reaction heterocyclic synthesis

Asymmetric Heck reaction in synthesis of heterocycles 97T7371. 

Synthesis of heterocycles using the intramolecular Heck reaction involving a formal nnd-elimination process 99H(51)1957. 

The double-Heck-approach can also be employed for the preparation of novel heterocyclic compounds as 6/1-25 and 6/1-26 (Scheme 6/1.4) [24]. Thus, the palladium-catalyzed reaction of 6/1-21 and the cyclic enamide 6/1-22 gave a Oil-mixture of 6/1-23 and 6/1-24, which in a second Heck reaction using the palladacene 6/1-15 led to 6/1-25 and 6/1-26 in an overall yield of 44—49%. The synthesis can also be performed as a domino process using a mixture of Pd(OAc)2 and the palladacene 6/1-15. 

Scheme 6/1.4. Double Heck-reaction for the synthesis of heterocycles.

A synthetically useful application of an intramolecular microwave-assisted Heck reaction has been described by Gracias and coworkers (Scheme 6.9) [28], In their approach toward the synthesis of N-containing seven-membered heterocycles, the... 

As will be seen in this chapter and in the rest of the book, the Heck reaction and its numerous variations represent a fantastically powerful set of tools available to the heterocyclic chemist. Although most Heck chemistry that involves pyrroles is intramolecular or entails synthesis of the pyrrole ring, a few intermolecular Heck reactions of pyrroles are known. Simple pyrroles (pyrrole, A-methylpyrrole, A-(phenylsulfonyl)pyrrole) react with 2-chloro-3,6-dialkylpyrazines under Heck conditions to give mixtures of C-2 and C-3 pyrrole-substituted pyrazines in low... 

The Heck reaction is applicable to the synthesis of benzo-fused heterocycles including indolines, 1,2-dihydroquinolines, and benzopyrans. Influence of reaction conditions on diastereoselectivity is witnessed in the cyclization leading to geissoschizol and its isomer. Reaction of 2-cyanothiophene with aryl halides introduces the aryl group to the 5-position."... 

The incredibly powerful and versatile Heck coupling reaction has found enormous utility in the indole ring synthesis and in the elaboration of this important heterocycle. Due to the enormity of this topic, the section is divided into Heck reactions of indoles, the synthesis of the indole ring as developed by Hegedus, Mori-Ban, and Heck, and the Larock indole ring synthesis. 

Hu et al. [104] disclosed that the spiro phosphine oxide ligand (/ )-30a is highly efficient for the Pd-catalyzed Heck reaction of cyclic and heterocyclic olefins with aryl triflates. An asymmetric domino Heck cyclization was established using catalyst Pd/(/ )-30a to form fused carbo- and heterocycles with excellent stereoselectivity (Scheme 42) [105]. This method was used in a short synthesis of (-)-martinellic acid, a primary ingredient in traditional eye medicine in South America. 

The intramolecular asymmetric Heck reaction has featured in the synthesis of complex heterocyclic compounds. Bidentate ligands, such as diphosphines (especially BINAP) and phosphine—oxazolines, have been used as a chiral ligand of the asymmetric Heck reaction. Imbos et al. demonstrated that the mono-dentate phosphoramidite 513 was an effective ligand for the asymmetric Heck reaction of the prochiral cyclohexadienone 511 (Scheme 153).227 The reaction of 511 in the presence of catalytic amounts of Pd-(OAc)2 and the chiral phosphoramidite 513 gave the 4a-methoxy-4a//-benzo[c]chromen-2(6E/)-one 512 in 71% yield with 96% ee. By contrast, the reaction of... 

Heterocycle synthesis. In the presence of HCOONa and with microwave irradiation Heck reaction of A -alkynoyl-2-(t)-brDmoaryl)ethylamines cyclize to give benzazepine derivatives. Benzannulated eight-membered lactam homologues are also accessible by the method. 

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