Reactivity of Woollins' Reagent toward 2‐En‐1‐imines (Schiff Bases): A Facile Approach to Synthesize New Selenium‐Phosphorus‐Nitrogen Heterocycles

Abstract

Woollins' Reagent serves as a reductive cycloaddition reagent, reacting with 2-en-1-imines containing a conjugated C=C bond group (Schiff bases) leading to a series of four-, five-, six-membered 1,2-azaphospholidines incorporating one [a] 4683 in these saturated phosphorus-nitrogen five-membered rings 2c-i (68.8-79.0 ppm). Scheme 4. Cycloaddition derivatives 2j of Schiff base 1j.

Recent advances in organophosphorus–chalcogen and organophosphorus–pincer based macrocyclic compounds and their metal complexes

“…The reaction between Schiff base derivatives (2-en-1-imines) and [PhP(Se)(μ-Se)] 2 led to the isolation of a series of four-, five-and six-membered 1,2-azaphospholidines containing one or two N-PvSe linkages, as shown in Schemes 10 and 11. 72 Heterocycles 22a and 22b were obtained from the reactions of the corresponding Schiff bases with [PhP(Se)(μ-Se)] 2 via [3 + 2] and [1 + 4] cycloaddition reactions, respectively (Scheme 10). A series of saturated five-membered heterocyclic rings 22c-i were also prepared in moderate to good yields (34-67%) by the reactions of substituted Schiff bases (having a conjugated CvC link) with [PhP(Se)(μ-Se)] 2 involving both cycloaddition and reduction reactions, as shown in Scheme 10.…”

“…However, the source of hydrogen responsible for the reduction process (for 22c-i) is not mentioned in the paper. 72 Surprisingly, under similar reaction conditions, the treatment of a Schiff base having a -SCH 3 group, attached to an aminophenyl ring, with [PhP(Se)(μ-Se)] 2 afforded an unexpected five-membered heterocycle 22j via a [2 + 3] cycloaddition reaction. The reaction pathways for the formation of compounds 22a-j can be described as follows: substitution of one of the bridging selenium atoms in [PhP(Se)(μ-Se)] 2 by the CvN group of the Schiff base resulted in five-membered heterocycle 22a, whereas the formation of 22b was due to the cycloaddition of a PvSe bond across the CvC-CvN bond involving a six-membered intermediate which eventually lost a Se atom.…”

Novel Five- and Six-Membered Rings of Phosphorus–Selenium Heterocycles from Selenation of Amido-Schiff Bases

“…The chemistry of 2,4-bis­(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide (Woollins’ reagent, WR) has been developed and exploited widely by us and other groups as a versatile selenation reagent or synthetic precursor in synthetic chemistry. − Recently, we have reported that Woollins’ reagent can add to the CN bond of a series of conjugated Schiff bases to generate a series of stable five-membered phosphorus–selenium–nitrogen heterocycles . In continuation of our interest in the chemistry of WR toward various organic substrates, we report herein the reactivity of WR toward amido-Schiff bases, which led to the formation of a series of five- and six-membered P–Se heterocycles and their related X-ray structures.…”

“…18−31 Recently, we have reported that Woollins' reagent can add to the CN bond of a series of conjugated Schiff bases to generate a series of stable five-membered phosphorus−selenium−nitrogen heterocycles. 32 In continuation of our interest in the chemistry of WR toward various organic substrates, we report herein the reactivity of WR toward amido-Schiff bases, which led to the formation of a series of fiveand six-membered P−Se heterocycles and their related X-ray structures. To the best of our knowledge, this is the first reported synthesis and single-crystal structures of such small ring phosphorus−selenium heterocycles incorporating single Se−PSe or N−PSe linkage.…”

Exo-trig selenocyclization of secondary allylic carboxamides using Woollins’ reagent: en route to 2,5-disubstituted selenazolines

“…This reagent has been explored for its selenating property in various substrates encompassing carbonyl compounds, double and triple C–C bonds, C–N triple bonds, and Schiff bases, among others, resulting in a wide range of products such as selenium heterocycles, selenoamides, selenoic Se-acids, and four–ten-membered selenophosphorus heterocycles. 3–5 Furthermore, its reductive potential has been explored in carbonyl and α,β-unsaturated compounds. 6 A few examples pertaining to the reactivity of WR are delineated in Fig.…”