Copper‐Catalyzed [3+2] Cycloaddition Reactions of Isocyanoacetates with Phosphaalkynes to Prepare 1,3‐Azaphospholes

Abstract

A novel copper‐catalyzed synthetic method is described for phosphorous‐ and nitrogen‐containing heterocycles such as 1,3‐azaphospholes. Cycloaddition reactions of various isocyanoacetates with phosphaalkynes in the presence of copper bromide, bis(diphenylphosphino)methane (dppm), and potassium carbonate afford the corresponding 1,3‐azaphospholes in high yields with complete selectivity. Some dppm‐bridged dicopper complexes were identified as active species for the formation of 1,3‐azaphospholes.

Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex

“…The training set used in this study is composed of 21 molecules containing C-P bonds for which experimental 1 J CP values have been reported: 5 with a C-P single bond, 56,57 6 with a double bond, [57][58][59][60][61][62] and 10 with a triple bond (see ESI † for more details). [63][64][65][66][67][68][69] Originally, exploring empirical corrections for a broader dataset of 1 J XY coupling-constant data, where X and Y are C, N, or P, was intended. However, unlike the coupled cluster data reported by Del Bene and coworkers, 41 experimental and computed DFT data for this level of atom generality were too poorly correlated for meaningful linear regression.…”

Copper‐Catalyzed [3+2] Cycloaddition Reactions of Isocyanoacetates with Phosphaalkynes to Prepare 1,3‐Azaphospholes

“…A small amount of isomeric product (3a' ')w as observed when dppe,PPh 3 ,and dtbpy were used as ligands (entries 6, 8, and 9). Finally,w ec onfirmed that the combination of CuBr, dppm, and K 2 CO 3 is necessary to obtain 3a in good yield (entries [10][11][12].…”

“…Thedetailed molecular structure of 3a was determined by X-ray crystallographic analysis, [12] and an ORTEP drawing is shown in Figure 1. To the best of our knowledge,single-crystal X-ray analyses on non-anellated 1,3-azaphospholes have not been reported, although some theoretical studies have revealed structures of 1,3-azaphospholes.…”

“…Detailed molecular structures of 4, 5,and 6 were determined by X-ray crystallographic analysis. [12] IR measurements of 5 and 6 were carried out to reveal the nature of coordinated 2a.Absorbance signals attributable to the C-N stretching of 2aon 5 and 6 were observed at 2188 and 2186 cm À1 ,r espectively.T hese values are higher than that of free 2a (2164 cm À1 ). In copper-isocyanide complexes,t he isocyanides have been known to work not only as a s donor but also as a p acceptor toward the Cu atom.…”

Isocyano(triphenylphosphoranylidene)acetates: Key to the One-Pot Synthesis of Oxazolo[4,5-c]quinoline Derivatives via a Sequential Ugi/Wittig/aza-Wittig Cyclization Process

“…Isocyanide compounds added an extra bonus for enlarging the repertoire of accessible molecular scaffolds and have found widespread use in multicomponent reactions, insertion reactions, and other one-pot cascade processes . Among the families, functionalized isocyanides with several reaction centers such as TosMIC, isocyanoacetates, and isocyanoacetamides have become more attractive in recent years and have proven to be a versatile functionality to react with carbonyl compounds, imines, activated alkenes/alkynes, and others . Nevertheless, groups like ester, amide, and tosyl on the isocyanides have not been sufficiently utilized in part of the reactions, as seen in investigation of the related literature.…”