A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

Abstract

SummaryEasily obtainable cyclic enaminones (piperidin-2-ylidenealkanones) can be transformed into substituted bicyclic pyridazinium tetrafluoroborates upon treatment with corresponding diazonium salts. The transformation can be performed either in a one-pot way or in a two-step process with the isolation of single azo-coupled enaminone as the intermediate. The former method is superior. Under the optimized conditions, a number of pyridazinium salts substituted with both electron-donating and electron-withdrawing substituents was easily synthesized. A mechanism of the formation of the pyridazinium salts is suggested. A partial drawback is the possibility of the formation of a mixture of products when using a different diazonium salt in each step due to a reversibility of the azo coupling. This can be suppressed by using a more reactive diazonium salt before a less reactive one.

From synthetic control to natural products: a focus on N‐heterocycles

“…Exocyclic vinylogous amides built on a piperidine ring are versatile intermediates in the preparation of many N ‐heterocycles and natural alkaloids (Fig. ), such as desoxoprosophylline, cassine, pinidinone, deoxyfebrifugine and norallosedamine, among others .…”

Synthesis and Characterization of New Boron Compounds Using Reaction of Diazonium Tetraphenylborate with Enaminoamides

“…We have studied the reactions of polarized ethylenes, such as β-enaminones, β-enaminonitriles, and β-enaminoamides, with substitution on the amino group, with diazonium salts, leading to heterocyclic compounds. These compounds are pyridazines [20][21][22], pyrazoles [23][24][25][26], oxazaborines, diazaborinones, and triazaborines [27][28][29][30][31]. In 2009, we published work on the reaction of β-enaminoamides 1 (Figure 1, R 3 = Ph) and 4-methylbenzenediazonium tetraphenylborate to give compounds I-III (Scheme 2) [28].…”

The Behavior of 3-Anilinoenone and N-Phenyl Cinnamamide toward Carbon Nucleophiles: Spectroscopy and X-Ray Studies Reveal Interesting New Synthesis Routes to Nicotinonitriles and Tetrahydropyridine-3- Carbonitrile

“…The chemistry of enaminones is recognized as a significant field of study because enaminones serve as both starting materials for the synthesis of various heterocyclic compounds that have potential agrochemical use [1][2][3][4][5][6][7][8][9][10] and as intermediates in dye and pharmaceutical industries [11][12][13][14][15]. Due to their biological activities and pharmacological properties, pyridines and pyridones represent an important class of compounds that have been developed using functionally substituted enaminones [16][17][18][19][20][21][22].…”