Pyridinium ylides derived from pyryliums and amines and a novel rearrangement of 1-vinyl-1,2-dihydropyridines

Abstract

Avermectin BIa Aglycon (8) and Monosaccharide (7). A mixture of 46.2 mL of H20,46.2 mL of concentrated H2S04, and 170 mL of THF was added over 30 min to a solution of 3 (22.2 g, 0.025 mol) in 200 mL of THF stirred in an ice bath. After the addition was completed, the reaction mixture was left at 18 °C for 24 h under a nitrogen atmosphere. Analysis by TLC and HPLC showed after 2 h about 60% of 3 and 40% of 7 and after 16 h about 60% of 7 and 40% of 8. It also showed that the product

Reactivity and stereoselectivity of oxazolopyridines with a ring‐junction nitrogen atom

“…Treatment of salts 186 with acetic anhydride afforded the corresponding acetates 187 . The styryl‐pyridinium salts 188 were obtained in good yields by refluxing 187 in pyridine (Scheme ) …”

“…The styryl-pyridinium salts 188 were obtained in good yields by refluxing 187 in pyridine (Scheme 37). [49]…”

Structure–activity relationship studies of SEN12333 analogues: Determination of the optimal requirements for binding affinities at α7 nAChRs through incorporation of known structural motifs

“…4-Bromobenzoyl chloride (0.25 g, 1.12 mmol) was suspended in CH 2 Cl 2 (10 mL) and cooled to 0 C. A solution of the crude amine (1.12 mmol) and triethylamine (156 mL, 0.8 mmol) in CH 2 Cl 2 (10 mL) was added dropwise and stirring continued at 0 C for 0.5 h. The mixture was then allowed to reach room temperature and stirring continued for a further 2 h. CH 2 Cl 2 (50 mL) was added and the solution washed with saturated aqueous sodium carbonate (50 mL), saturated aqueous ammonium chloride (50 mL 140.3, 133.8, 129.0, 128.0, 127.6, 127.3, 127.2 [63]. To a solution of pyridine (323 mL, 4.0 mmol) in dichloromethane (20 mL) was added trifluoroacetic acid (308 mL, 4.0 mmol) followed by 4-nitrophenylboronic acid (51) (2.0 g, 12.0 mmol).…”

Reactions of pyridinium ylides with aldehydes and with Michael acceptors

“…The classic work of Krohnke ' established that the pyridinium ylides (2) derived from N-alkyl-, N-allyl-, and N-benzylpyridinium salts (1) react with electrophiles to give synthetically useful adducts (3). However, deuterium-hydrogen exchange is faster at the C-2 and C-6 protons than at the a-CH, group of (la) and (lc).…”