Heck-type coupling

The dipyrrylacelylenedicarbaldehyde 18, which already contains, along with the acetylene moiety, two of the two-carbon bridges of the final macrotetracycle, can be prepared by a Heck-type coupling of 5-iodopyrrole-2-carbaldehydes with acetylene.8a,b The main conjugation pathway with 22n electrons is already present in the acetylene-cumulate systems 19. The expected planarity of this chromophore has been confirmed by X-ray structure analysis.8a b... 

Water-soluble phosphine ligands containing m-guanidinium moieties were synthesized and applied to aqueous Heck coupling reactions.149 High temperature appears beneficial for Heck-type coupling of simple alkenes in water.150... 

Rhodium-catalyzed Heck-type coupling of boronic acids with activated alkenes was carried out in an aqueous emulsion.82 The couplings between arylboronic acids and activated alkenes catalyzed by a water-soluble tm-butyl amphosrhodium complex were found to progress at room temperature to generate Heck-type products with high yields and excellent selectivity. It was necessary to add two equivalents of the... 

Polycyclic aromatic hydrocarbons such as fluoranthrene or Cso-fullerene are structures of great interest A straightforward entrance to analogues and partial structure, respectively, has now been developed by de Meijere and coworkers [89], using a combination of a Suzuki and a Heck-type coupling. Thus, reaction of 1,8-dibromophenanthrene 6/1-166 and obromphenylboronic acid 6/1-167 employing 20 mol% of the Pd° catalyst led to 6/1-168 and 6/1-169 in 54% yield as a Id-mixture (Scheme 6/1.45). 

Another contribution involving formation of the six-membered ring was reported by Dominguez <20030L1095>. In this case, the key step involves a biaryl Mizoroki-Heck-type coupling. Fair yields (42-65%) of pyrazolophenan-thridines 20 can be obtained from easily available starting materials prepared from acetophenones and hydrazines (Scheme 9). 

Traditional Stille-type (49 + 50 -> 51 <998615>) and Heck-type couplings (52 S3 <99JHC145>) of halopyrimidines were also well represented. The latter reaction was utilized enroute to a new class of dihydrofolate reductase inhibitors 53. 

In the first reported solid-phase Richter reaction, cinnolines 143 were prepared through a two step sequence of a Heck-type coupling to give intermediates 142 followed by intramolecular ring formation and release of ciimolines 143 <99TL6201>. 

Yoshida and co-workers have reported on the use of alkenyldimethyl(2-pyridil)silanes as versatile platforms for olefin synthesis.The combination of Mizoroki-Heck-type coupling and Hiyama cross-coupling provided a diverse range of stereodefmed polysubstituted olefins. 

The same transformation has also been extended to pyridone-type systems, where the ring closure might also be described as a Heck-type coupling. Padwa reported the conversion of condensed 3-(o-bromoanilino)-... 

The intramolecular version of Heck-type couplings was investigated for the first time in water, which led to a dramatic change in regioselectivity (118). With water-soluble Pd/tppts catalysts, the generally observed exo... 

The formation of compound 175 could be rationalized in terms of an unprecedented domino allene amidation/intramolecular Heck-type reaction. Compound 176 must be the nonisolable intermediate. A likely mechanism for 176 should involve a (ji-allyl)palladium intermediate. The allene-palladium complex 177 is formed initially and suffers a nucleophilic attack by the bromide to produce a cr-allylpalladium intermediate, which rapidly equilibrates to the corresponding (ji-allyl)palladium intermediate 178. Then, an intramolecular amidation reaction on the (ji-allyl)palladium complex must account for intermediate 176 formation. Compound 176 evolves to tricycle 175 via a Heck-type-coupling reaction. The alkenylpalladium intermediate 179, generated in the 7-exo-dig cyclization of bro-moenyne 176, was trapped by the bromide anion to yield the fused tricycle 175 (Scheme 62). Thus, the same catalytic system is able to promote two different, but sequential catalytic cycles. 

Intramolecular Heck reaction of organomercurial 332 has been used to prepare unsaturated lactone 333 by a non-traditional strategy452. Sequential, regiospecific C—C and C—N bond-forming reactions via a novel Heck-type coupling have been developed453. 

A similar procedure was employed in the asymmetric Heck-type coupling of iodonium salt 81 with 2,3-dihydrofuran (Scheme 38) [65]. When carried out in the presence of the chiral bidentate ligand (R)-BINAP, this reaction afforded optically active (up to 78% ee) coupling product 82 in moderate yield. 

A direct Heck-type coupling of 2-furaldehyde with various electron-rich and electron-deficient aryl iodides and bromides to provide 5-aryl-2-furaldehydes regioselectively was also developed <20010L1677>. An interesting example is shown in Equation (36). 

A Heck-type coupling of 2,3-dihydrofuran with a secondary chloroacetamide produced the two double bond isomers in about 2 1 ratio <03TL5751>. A palladium-catalyzed Heck-type coupling between the heterocyclic iodide shown below and 2,3-dihydrofuran was used as Ae key step in the synthesis of C-nucleosides. Conditions were optimized to include AgjCOj to prevent double migration and thereby obtain a good yield of the desired 2,5-dihydrofuran products <03JMC1449>. 

An Al-acyl-(3-keto derivative has been prepared by reaction with a diketene equivalent and the tranj-N-cinnamoyl derivative by a Heck type coupling reaction. The A-fluoro derivative (3) is prepared by direct fluorination (eq 2). ... 

The synthetic potential of these catalysts has been investigated in Heck-type coupling reactions treatment of l-bromo-4-nitrobenzene with n-butyl acrylate in isopropyl alcohol in the presence of 2.5 mol% of catalyst and tetrabutylammonium acetate afforded the unsaturated ester in an excellent... 

Heck-type coupling of allylic alcohols and enol triflates.- This vinylation of allylic alcohols can be effected by catalysis with Pd(OAc)2 and tri-o-tolylphosphine (1 2) and triethylamine (excess) as base. The major products arc conjugated dicnols. 

Scheme 41. Representative Exzimple for Dipyridyl Amide-Functionalized Polymer Beads for the Selective Binding of Hg(II) and Pd0I) Prepared via Ring-Opening Metathesis Precipitation Polymerization and for the Preparation of Heterogeneous Supports for Heck-Type Couplings, Respectively ...

Buchwald-Hartwig Amination Followed by Heck-Type Coupling (Pd[0]/Pd[01)... 

Scheme 45 Synthesis of carbazoles 32 by Buchwald-Hartwig amination and subsequent cyclization by intramolecular Heck-type coupling of the intermediate diarylamines 197...

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