1-Imidoalkylphosphonium salts with modulated Cα-P+ bond strength: synthesis and application as new active α-imidoalkylating agents

Jakub Adamek; Roman Mazurkiewicz; Anna Węgrzyk; Karol Erfurt

doi:10.3762/bjoc.13.142

1-Imidoalkylphosphonium salts with modulated C_α-P⁺ bond strength: synthesis and application as new active α-imidoalkylating agents

Beilstein J Org Chem. 2017 Jul 24:13:1446-1455. doi: 10.3762/bjoc.13.142. eCollection 2017.

Authors

Jakub Adamek^{1

2}, Roman Mazurkiewicz^{1

2}, Anna Węgrzyk^{1

2}, Karol Erfurt³

Affiliations

¹ Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Silesian University of Technology, B. Krzywoustego 4, 44-100 Gliwice, Poland.
² Biotechnology Centre of Silesian University of Technology, B. Krzywoustego 8, 44-100 Gliwice, Poland.
³ Department of Chemical Organic Technology and Petrochemistry, Silesian University of Technology, B. Krzywoustego 4, 44-100 Gliwice, Poland.

Abstract

An effective synthesis of the hitherto unknown 1-imidoalkylphosphonium salts has been developed in the reported study. The crucial step in the method included the decarboxylative α-methoxylation of N-phthaloyl- or N-succinylamino acids to the corresponding N-(1-methoxyalkyl)imides, followed by the displacement of the methoxy group by the triarylphosphonium group through melting of the imide derivative with triarylphosphonium tetrafluoroborate. The imidoalkylating properties of the obtained 1-imidoalkylphosphonium salts were tested using the Tscherniac-Einhorn-type reaction with aromatic hydrocarbons as a model reaction. It was found that the C_α-P⁺ bond strength can be considerably reduced and the imidoalkylation of arenes can be markedly facilitated using 1-imidoalkylphosphonium salts derived from triarylphosphines with electron-withdrawing substituents such as tris(m-chorophenyl)phosphine, tris(p-chlorophenyl)phosphine and tris[p-(trifluoromethyl)phenyl]phosphine. Microwave irradiation also considerably facilitates the cleavage of the highly polar C_α-P⁺ bond.

Keywords: 1-imidoalkylphosphonium salts; N-(1-arylalkyl)imides; Tscherniac–Einhorn-type reaction; imidoalkylation reactions; α-imidoalkylating agents.