Transition metal-catalyzed cross-coupling reactions of functionalized organometallic reagents
In summary, reaction conditions have been found for a versatile nickel-catalyzed crosscoupling reaction in the presence of an electron deficient styrene promoter, allowing for the first time: · effective coupling of readily available functionalized alkylzinc halides and benzylic zinc bromides with functionalized alkyl iodides in the presence of TBAI · the application of alkyl bromides in a Csp3-Csp3 cross-coupling reaction. Furthermore, · the presence of sensitive functional groups such as an amino function with an unprotected NH group is tolerated · coupling of diastereomerically enriched zinc reagents proceed with high retention of configuration at the zincated carbon · scaling up can be achieved without significant loss of chemical yield. In summary, an effective and high yielding protection-deprotection protocol has been developed for the iodine-magnesium exchange reaction of 2-iodo-1,4-phenylenediamine. The corresponding 2-magnesiated-1,4-phenylenediamine derivatives can be transmetallated either to copper: · a subsequent allylation reaction furnishes the allylated products in good yield, or to the corresponding zinc reagents: · a subsequent smooth palladium-catalyzed cross-coupling reaction with a range aryl iodides furnishes the polyfunctionalized cross-coupling products in good yield, · this cross-coupling reaction is highly tolerant towards electronic as well as steric effects.
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