Iron catalyzed coupling

Oxidation of /U-cresol afforded a triphenol 22 which is approximately half the molecule. The central hydroxyl of the triphenol could be selectively methylated and then the compound was ort/ro-brominated and bridged using 1,3-dibromopropane to give 23. Metallation with butyllithium followed by iron catalyzed coupling afforded the macrocycle as indicated. 

TABLE 4. Iron-catalyzed coupling of Grignard reagents with alkenyl bromides... 

Surprisingly, when the same authors started from a 6,8-dichloropurine derivative, the course of the reaction depended on the reagent. Phenylboronic acid showed a marked preference for the 6-position again, while the iron catalyzed coupling of methylmagnesium chloride proceeded selectively in the 8-position (8.3.), The rationale behind the observed selectivity is still unclear.8... 

Figure 6.2 Bica and Gaertner [34] used a first-generation IL to carry out a biphasic iron-catalyzed coupling.

Fig. 8 Iron-catalyzed coupling reactions of P-dicarbonyl compounds with ethers, sulfides or tertiary amines...

Begtrup and co-workers employed iron-catalyzed coupling to prepare pyrrolidine RCM-precursors <02SL1889> (Scheme 11) while Grigg and co-workers employed a palladium-... 

Grignard reagents couple with aryl hahdes without a palladium catalyst, by the benzyne mechanism, but an iron catalyzed coupling reaction was reported, " as... 

At the same time, he reported an iron-catalyzed coupling process [429,431]. Alkyl-bromide showed disproportionation, rather than coupling [Eqs. (189) and (190) ... 

The path to the discovery of the reactions described herein was circuitous and unpredictable. It was spurred by serendipity, the thrill of scientific explora-tiOTi and the drive that accompanies any competitive process. Someday, future chemists will likely look back and be amazed at how little we new about the reactivity of C—H bonds, iron-catalyzed coupling reactions, etc., just like we look at Hmidius map and are instantly drawn to its errors. The scientific process has always been turbulent, but it is an exceedingly gratifying adventure. 

Scheme 39 Iron-catalyzed coupling of pyridines with arylboronlcacids.

Iron-catalyzed coupling between phenylmagnesium bromide and 2-bromobutane... 

Accordingly, iron-catalyzed coupling of tricyclo[4.1.0.0 ]hept-l-ylmagnesium bromide and related Grignard reagents with propargylic halides proceeds either in an overall Sn- or Sn fashion depending on the substitution pattern of the alkyne (Scheme 4-204). Terminal alkynes predominantly afford allenes via a Sn route, whereas trimethylsilyl-substituted alkynes lead to alkyne derivatives. ... 

Scheme 4-208. Iron-catalyzed coupling of aryl Grignard reagents with...

Scheme 4-223. Biaryls by iron-catalyzed coupling of aryl cuprates with or// o-carbamoyl-substituted aryliodides or 8-iodoquinolinones.

Alternatively to Grignard reagents, diorganozinc compounds can also be introduced in iron-catalyzed coupling reactions with acyl chlorides to provide a wide range of polyfunctional ketones under mild reaction conditions. ... 

---