A simple and efficient synthesis of 2,- 3-, or 4-(2-nitrophenyl)pyridine derivatives via palladium catalyzed ullmann cross-coupling reaction

Total synthesis of (±)-rhazinal, an alkaloidal spindle toxin from Kopsia teoi

“…The readily derived tosylate 13 (76%) was then subjected to dibromocarbene addition under phase transfer conditions and in this manner the gem-dibromocyclopropane 14 was obtained in 70% yield. Reaction of this last compound under solvent free conditions with the sodium salt of 2-nitrophenylated pyrrole 15, 7 readily derived via a Pd[0]-catalysed Ullmann cross-coupling 28 of o-nitrobromobenzene with methyl 4-iodo-1H-pyrrole-2carboxylate, 29 then afforded the target substrate 4 (X = NO 2 , Y = CO 2 Me) (quantitative) required for examination of the pivotal cyclisation step. In the event, all attempts, including those involving the use of silver salts and/or the application of heat, failed to effect electrocyclic ring-opening of cyclopropane 4 (X = NO 2 , Y = CO 2 Me) and consequent formation of target 5.…”

Palladium‐Catalyzed Intramolecular Reductive Cross‐Coupling of Csp2Csp3 Bond Formation

“…Palladium‐catalyzed reductive coupling, which was reported by Shimizu et al. in 1993,6 has been proved to be an effective protocol in the preparation of the Csp 2 Csp 2 bond as well 7. However, these products were restricted to homocoupling ones.…”

Palladium‐Catalysed Cross‐Coupling and Related Reactions Involving Pyrroles

“…We have recently reported on the application of the title process130 to the preparation of indoles131 and quinolines,132 but our efforts in this area originated from the observation117b (Scheme ) that methyl 4‐iodopyrrole‐2‐carboxylate ( 98 ) can be cross‐coupled with 2‐bromonitrobenzene ( 128 ) in the presence of copper bronze and catalytic quantities of Pd(PPh 3 ) 4 to give the 4‐arylated pyrrole 129 in 88 % yield at 48 % conversion. It is worth noting that when this sort of reaction is performed in the absence of a palladium catalyst then the only product of reaction is 2,2′‐dinitrobiphenyl arising from reductive homo‐coupling of compound 128 .…”