1-(N-Acylamino)alkyltriarylphosphonium Salts with Weakened Cα-P+ Bond Strength—Synthetic Applications

Abstract

The α-amidoalkylating properties of 1-(N-acylamino)alkyltriarylphosphonium salts with weakened Cα-P+ bond strength are discussed and examined. It is demonstrated that such type of phosphonium salts reacts smoothly with a diverse array of carbon- and heteroatom-based nucleophiles, including 1-morpholinocyclohexene, 1,3-dicarbonyl compounds, benzotriazole sodium salt, p-toluenesulfinate sodium salt, benzylamine, triarylphosphines, and other P-nucleophiles. Reactions are conducted at room temperature, in a short time (5–15 min) and mostly without catalysts. Simple work-up procedures result in good or very good yields of products. The structures of known compounds were established by spectroscopic methods and all new compounds have been fully characterized using 1H-, 13C-, 31P-NMR, IR spectroscopy, and high-resolution mass spectrometry. Mechanistic aspects of described transformations are also performed and discussed. It was demonstrated that unique properties make 1-(N-acylamino)alkyl-triarylphosphonium salts with weakened Cα-P+ bond strength interesting building blocks with great potential, especially in α-amidoalkylation reactions.

Michaelis-Arbuzov-Type Reaction of 1-Imidoalkyltriarylphosphonium Salts with Selected Phosphorus Nucleophiles

“…Based on our previous research [32,33,34,35,36] and above-described facts, we proposed a plausible mechanism of the Michaelis-Arbuzov-type reaction of 1-imidoalkylphosphonium salts with phosphorus nucleophiles (Scheme 3). It seems that the first stage is crucial for the course of the entire reaction.…”

“…Then, we investigated the effect of molar ratio of substrates and the type of solvent on the reaction yield (entries 1–5, Table 1). It should be noted that one of the Michaelis-Arbuzov reaction stages is dealkylation of the alkoxyphosphonium salt 4 (see Scheme 3) [34,35]. To facilitate the course of this step, we used methyltriphenylphosphonium iodide as the catalyst (iodide anions are a good dealkylating agent) [34,35,36].…”

1-Aminoalkylphosphonium Derivatives: Smart Synthetic Equivalents of N-Acyliminium-Type Cations, and Maybe Something More: A Review

“…The last step is the substitution of the methoxy group in the reaction of N , O -acetals 30 with various types of phosphonium salts (Ar 3 P·HX, Scheme 7 ; Method A). The proposed method allows high yields (up to 99%) to be obtained not only for the simplest 1-( N -acylamino)alkylphosphonium salts 4 (e.g., R 2 = H), but also for much more complex structure, including derivatives of phosphine with various substituents (Ar = Ph, 3-C 6 H 4 Cl, 4-C 6 H 4 CF 3 ) [ 43 , 46 ]. Moreover, the raw material base can be expanded, since N -methoxyalkyl derivatives can be obtained by electrochemical oxidation of amides, carbamates or lactams.…”

“…The strength of the C α -P + bond can be further reduced by introducing electron-withdrawing substituents to the phosphonium moiety ( Scheme 10 , Ar = 3-C 6 H 4 Cl and 4-C 6 H 4 CF 3 ). The equilibrium in such systems was examined and described in 2018 [ 46 ]. As can be seen, it is shifted toward more stable and less reactive 1-( N -acylamino)alkylphosphonium salts (reactivity: PS-CF 3 > PS-Cl > PS-H; stability: PS-CF 3 < PS-Cl < PS-H).…”

Non-Kolbe electrolysis of N-protected-α-amino acids: a standardized method for the synthesis of N-protected (1-methoxyalkyl)amines

“…11 The main reason for this is the ease of forming new C-C and C-heteroatom bonds (e.g., C-P, C-S, C-N) via both intermolecular a-amidoalkylation and intramolecular cyclization, leading to carbo-and heterocyclic compounds. 11,[15][16][17][18][19]…”