Heck approach

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. 

Using a different catalytic system, the Larhed group was able to perform regio-selective microwave-promoted chelation-controlled double-/3-arylations of terminal alkenes (Scheme 6.5) [24]. In this Heck approach, the authors used vinyl ethers as chelating alkenes and aryl bromides as coupling partners, employing Herrmann s... 

Lastly, a formal synthesis of almotriptan (5) has been published by the Bosch group in Spain using an intramolecular Heck approach (Scheme 23). lodination of aniline 58 with bis(pyridine)iodonium(I) tetrafluoroborate followed by reaction with trifluoroacetic anhydride (TFAA) gave the o-iodotrifluoroacetanilide 66. Alkylation of 66 with methyl 4-bromocrotonate afforded 67, which underwent palladium catalyzed... 

A novel, two-step RCM-Heck approach to bridged N-heterocycles was reported by Grigg and York, one example of this methodology being shown in Scheme 36 <00TL7255>. In the case shown, the yield is 69% when the reactions are run separately, 37% when the reactions are run in combination using Pd(OAc)2, and 73% when PS-Pd is employed in a two-step, one-pot procedure. 

Scheme 8. Synthesis of resverafrol using a direct decarbonylative Heck approach...

During the study 5 other novel arylbenzofiiran analogues were also synthesised along with the key stilbenes which were synthesised by Wittig and Heck approaches [73,74]. 

Scheme 7 Heck approaches towards Cinacalcet hydrochloride...

DSM produces the antioxidant Resveratrol, the component in red wine that is responsible for a number of positive health effects also known as The French paradox . They have published a total synthesis of Resveratrol that is based on a Heck approach using acetylated intermediates (Scheme 13) [48, 49]. The best yield (94%) and highest substrate/catalyst ratio (2,000) were achieved using the palladacycle catalyst developed by Najera and co-workers [49, 50]. Hydrolysis of the tris-acetate provided Resveratrol in good yield. 

Also a multitude of novel heterocyclic compounds, such as 25 and 26, can be prepared by a double Mizoroki-Heck approach [23]. Thus, the palladium-catalysed reaction of 21 and... 

As detailed in Scheme 1, the intramolecular Heck approach began by protecting para-chlorophenylethylamine (9) as its corresponding trifluoroacetamide 10. lodination of 10 may be achieved in couple of alternatives either with iodine monochloride or with its more sophisticated cousin bis(pyridine)iodonium(I) tetrafluoroborate to furnish iodide 11. Iodide 11 was aUylated to afford 12, which underwent an intramolecular Heck... 

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