MoCl₅ as an effective chlorinating agent towards α-amino acids: synthesis of α-ammonium-acylchloride salts and α-amino-acylchloride complexes

Abstract

The reactivity of MoCl5 with α-amino acids was investigated for the first time by choosing CH2Cl2 as the reaction medium. The interaction of MoCl5 with l-proline proceeded with Cl/O interchange and led to the formation of [NH2(CH2)3CHC(O)Cl][MoOCl4], 1, in 63% yield. The reactions of MoCl5 with l-phenylalanine, sarcosine, N,N-dimethylglycine and N,N-dimethyl-l-phenylalanine afforded the α-amino-acylchloride complexes MoOCl3[O[double bond, length as m-dash]C(Cl)CH(R)N(R')(R'')] (R = CH2Ph, R' = R'' = H, 2a; R = R' = H, R'' = Me, 2b; R = H, R' = R'' = Me, 2c R = CH2Ph, R' = R'' = Me, 2d), in ca. 70% yields. According to DFT studies, 2a,d are mononuclear Mo(v) octahedral complexes bearing a N,O-coordinated α-amino-acylchloride ligand. The presumed species formed during the first stages of the MoCl5/l-phenylalanine interaction were DFT-elucidated, thus the calculated Gibbs free energy profile for the multi-step reaction of MoCl5 with l-phenylalanine was traced. [NH3CH(CH2Ph)C(O)Cl][MoOCl4], 3, acting as an intermediate in the course of the formation of 2a, was isolated by combination of [NH3CH(CH2Ph)C(O)Cl][Cl] with MoOCl3.

Light-Initiated C–H Activation via Net Hydrogen Atom Transfer to a Molybdenum(VI) Dioxo

“…Similarly, MoCl 5 can perform chlorinations of arenes that are proposed to occur through a single electron transfer mechanism. 88,89 Thus, by analogy to both CrO 2 Cl 2 and Mo(V) reactivity, in combination with observed product distributions and kinetic trends, 1* is well positioned to initially perform electron transfer reactions en route to a net HAT mechanism (Figure 7).…”

“…The resulting radical cation undergoes an attack on a second equivalent of arene to form the C–C bond followed by a series of ill-defined proton and hydrogen atom losses. Similarly, MoCl 5 can perform chlorinations of arenes that are proposed to occur through a single electron transfer mechanism. , …”

Diiron bis‐cyclopentadienyl complexes as transfer hydrogenation catalysts: The key role of the bridging aminocarbyne ligand

“…Extensive decomposition was detected after 10 h of thermal treatment of [1a]CF 3 SO 3 and 4a; however, chloride transfer from 4a to the organic substrate should be excluded. [63,64] Overall, results highlight the superior stability of the cyanide complex 3a under the experimental conditions employed in catalysis; therefore, 3a is assumed to behave as the active species in the TH reaction.…”

“…Extensive decomposition was detected after 10 h of thermal treatment of [1a]CF 3 SO 3 and 4a ; however, chloride transfer from 4a to the organic substrate should be excluded. [ 63,64 ]…”

Trapping carbamates of α-Amino acids: One-Pot and catalyst-free synthesis of 5-Aryl-2-Oxazolidinonyl derivatives

“…their water solubility, relative non-toxicity, structural diversity provided by the side chain, and the presence of a chiral center. Therefore, their use as precursors of valued-added chemicals has witnessed a highly growing interest [16][17][18][19][20][21][22]. In particular, "tailor-made" α-amino acids have been regarded as essential components of modern medicinal chemistry, and indeed a significant fraction of small molecular drugs comprise amino-acidic residues [16,23].…”