A predictive model for additions to N-alkyl pyridiniums

Abstract

Disclosed in this communication is a thorough study on the dearomative addition of organomagnesium nucleophiles to N-alkyl pyridinium electrophiles. The regiochemical outcomes have observable and predictable trends associated with the...

Regioselective Morita-Baylis-Hillman Reaction with N-Alkylpyridinium Salts as Electrophiles

“…In addition to the challenge of breaking the aromaticity, an important issue related to the nucleophilic addition to Nactivated pyridines is controlling the regioselectivity of the reaction, which may take place at either C-2 or C-4 position of the ring. 14 Herein, we describe our work on the MBH reaction using N-alkylpyridinium salts as electrophiles, which proceeds with high efficiency and excellent regioselectivity, depending on the structure of the electrophile (Scheme 1c).…”

Gold(I)‐Catalyzed Nucleophilic Allylation of Azinium Ions with Allylboronates

“…These are powerful reactions to access partially saturated nitrogen heterocycles, which are valuable chemical building blocks [5, 6] . Nucleophilic allylations of in situ‐generated N ‐acylazinium ions have also been explored, [7] typically using allyltin, [7a–e,g,j,m,n] allylindium, [7h,j,l,m] allylmagnesium, [7a,b,p,q] allylzinc, [7m] or allylsilicon reagents. [7i–k, ° ,p] However, these reactions are somewhat limited in scope and often lead to mixtures of regioisomeric products favoring those of addition to the 2‐ or 6‐positions.…”

Regioselective Asymmetric Alkynylation of N-Alkyl Pyridiniums

“…Recently, our research group became interested in the synthesis of biologically active alkaloids through the dearomatization of heterocyclic aromatic starting materials . For example, (+)-lupinine ( 1 ) was envisioned to arise from dihydropyridine 5 , which would be derived from the dearomative coupling of alkyne 7 and pyridinium 6 (See Figure B). − One example of this type of asymmetric dearomative alkynylation was demonstrated by Charette in 2001, exploiting a chiral iminoyl group to activate the pyridine ( 8 ) electrophile .…”