Date of Degree
Mark R. Biscoe
Chemistry | Organic Chemistry
alkyl nucleophiles, cross-coupling, Nickel-catalyzed, organic reactions
In the first chapter, introduction of transition metal-catalyzed cross-coupling reactions has been given. These transition metal-catalyzed C-C bond forming reactions have been used extensively in organic synthesis. Among them, C(sp2)-C(sp2) bond forming reactions have been widely studied over decades. More recently, some reports have demonstrated the use of C(sp3) nucleophiles and electrophiles in cross-coupling reactions. However, use of secondary and tertiary alkyl nucleophiles has remained a challenge due to competitive β-hydride elimination and slow transmetallation of bulky secondary and tertiary alkyl organometallic nucleophiles.
In the second chapter, the first general nickel-catalyzed Negishi reaction for the cross-coupling of unactivated, acyclic secondary alkylzinc halides and aryl and hetero-aryl iodides has been reported. This process is the first to overcome the β-hydride elimination problem inherent to the use of the analogous palladium-catalyzed processes. This method is very general and tolerates a wide range of functional groups. A detailed study of the effect of salt additives on these reactions has also been presented.
In the third chapter, this work has been extended to the use of tertiary alkyl nucleophiles and the first metal-catalyzed Kumada cross-coupling reaction of tertiary alkylmagnesium halides and aryl bromides/triflates has been reported. This reaction has very wide substrate scope, and vinyl bromides and vinyl chlorides can also be employed as electrophiles. Here, the effect of catalyst hydration on the reaction yield and selectivity has been demonstrated.
In the fourth chapter, a mild palladium-catalyzed reaction for the monoborylation of primary alkyl halides using bis(pinacolato)diboron as the boron source has been reported. This reaction is very general and can accommodate a wide range of functional groups. To increase the utility of this process, the crude borylation product has been converted into the corresponding boronic acid, trifluoroborate salt and another boronic ester. Aditionally, bis(neopentylglycolato)diboron has also been employed as the boron source.
Ajit Joshi, Amruta, "Nickel-catalyzed cross-coupling reactions involving secondary and tertiary alkyl nucleophiles" (2014). CUNY Academic Works.