Pyridylic anions are soft nucleophiles in the palladium-catalyzed C(sp³)–H allylation of 4-alkylpyridines

Abstract

We report a mild palladium-catalyzed method for the selective allylation of 4-alkylpyridines in which highly basic pyridylic anions behave as soft nucleophiles.

Coordination‐Controlled Nickel‐Catalyzed Benzylic Allylation of Unactivated Electron‐Deficient Heterocycles

“…The coordination‐controlled deprotonation with Zn(TMP) 2 revealed through these calculations has been previously underappreciated and may be applicable to other contexts. One benefit of the exquisite selectivity afforded through this mechanistic manifold is that the allylation proceeds in a predictable fashion when there are multiple benzylic positions [6c, 7b] …”

“…The diamidophosphite ligand was essential for the reactivity and enantioselectivity. More recently, Orellana and co‐workers [7b] realized Pd‐catalyzed allylation of 4‐alkylpyridines through conversion to alkylidene dihydropyridines. In addition to Pd catalysts, elegant alternative approaches employing Ir [8, 9] and Rh [10] catalysts have emerged more recently.…”

Site‐Selective Pyridylic C−H Functionalization by Photocatalytic Radical Cascades

“…We began our investigations by irradiating a mixture of pyridinium salts 1 , Langlois reagent 2 a , and alkene 4 a in the presence of a photocatalyst Q 1 to demonstrate the envisioned cascade reactions (Table 1). Based on the previous studies, [8a, 10, 11b] we first designed various R groups and investigated the reactivity of pyridinium salts 1 (see the Supporting Information for more details). When N ‐substituents such as R=CO 2 Et ( 1 ad ), SO 2 Ph ( 1 ae ), or SO 2 CF 3 ( 1 af ) were employed, we were unable to observe desired product 5 a (entry 1).…”

Mild Installation of Piperidines on 4-Alkylpyridines

“…We have uncovered some intriguing reactivity and regioselectivity patterns during our substrate scope study (Figure ). As we have detailed previously, − 2-alkylpyridines are not suitable nucleophiles because the corresponding ADHPs cannot form ( 12 ). Surprisingly, although the ADHPs from 4-isopropyl- and 4-benzylpyridine form readily ( 13 and 14 , respectively), they do not add to pyridine, presumably due to steric effects in the case of 13 and enhanced stability due to extended conjugation in the case of 14 (Figure a).…”