Reactivity and selectivity of N-vinylic λ⁵-phosphazenes towards electrophiles. Synthesis of 2-aza-1,3-dienes

Abstract

The reactivity of the P=N double bond of the N-vinylic h5-phosphazene (1) towards several electrophiles is reported. Intermolecular aza-Wittig reaction of Wphosphazene (1 ) with aldehydes, phenyl isocyanate, and acid anhydrides leads to ethoxycarbonyl 2-aza-l,3-dienes (3), conjugated carbodi-imides (4), and N-protected amino acrylic acid derivatives ( 5 ) , respectively, while the Z-azahexa-l,3,5-triene (8) and also the pyridine (7) are obtained when dienyl h5-phosphazenes (6) are used. Reaction of h5-phosphatene (1) with methyl iodide and acetyl chloride leads t o N-alkylated (10) and N-acylated derivatives (11 ), respectively. Treatment of compound (1 1 ) in the presence of amino derivatives affords 1 -amino-2-azabuta-l,3-dienes (14).

Synthesis and SAR of 5,6-diarylpyridines as human CB1 inverse agonists

“…Based on analogy to the Sanofi pyrazole and our pyridine scaffold, it was also of interest to prepare a series of 2-amido-5-(4-chlorophenyl)-6-(2,4-dichlorophenyl) pyridines (29a-i, Table 4) to see if the 2-substitution improved binding compared to the 3-amido series 20a-d. 18 In an independent synthesis (Scheme 4), 4-chlorocinnamic acid (21) was reduced to the alcohol 22 via formation of the mixed anhydride and subsequent reduction with sodium borohydride. 19 Swern oxidation of 22 afforded the aldehyde 23, which was treated with ethyl azido acetate 24 to provide the ethyl 2-azido-5-phenylpenta-2,4-dienoate 25.…”

“…20 Conversion to the pyridine ring was accomplished by stirring 25 overnight with triphenylphosphene to provide phosphazene 26, which was subsequently reacted with 2,4-dichlorobenzaldehyde (27) at 60°C to provide the desired 2-substituted pyridine scaffold as the methyl ester intermediate 28. 21 Utilizing previously described chemistry, a series of amides 29a-i were similarly prepared (Table 4). …”

Facile synthesis of 2‐alkylthio‐3‐amino‐4 H‐imidazol‐4‐ones and 2H‐imidazo[2,1‐b]‐1,3,4‐thiadiazin‐6(7H)‐ones via N‐vinylic iminophosphorane

“…To a solution of vinyliminophosphorane 1 [20][21][22] (5 mmol) in dry methylene chloride (15 mL) was added excess carbon disulfide (5 mL). After the reaction mixture was refluxed for 28 h, the solvent was removed under reduced pressure and ether/petroleum ether (1:2, 20 mL) was added to precipitate triphenylphosphine sulfide that was removed by filtration.…”

N-Vinylic Phosphazenes. A Useful Tool for the Synthesis of Acyclic and Heterocyclic Compounds

“…Aza-Wittig reaction of dienyl phosphazenes 8b gave 2-azahexa-1,3,5-triene 68, and subsequent 6 -electrocyclization of these compounds 68 led to the formation of pyridine 69 (Scheme 26) [34]. In this context the aza-Wittig reaction of N-vinylic phosphazenes derived from -amino acids have been used for the synthesis of heterocycles as pyridine derivatives 69.…”