1-Organosulfonyl-2-sila-5-piperazinones: Synthesis, molecular and crystal structure, and chemical transformations into 2-aminoacid derivatives

•New silacyclanes, 1-organosulfonyl-2-sila-5-piperazinones (2), are isolated.•Lability of the Si–N bond in 2 is utilised in various synthetic applications.•Disiloxanes (3), fluorosilane (4) and silyloxonium ions (6,8) are prepared from 2.•X-ray structures of nine tetra- and pentacoordinate silicon compounds are reported.

The reaction of chloro(chloromethyl)dimethylsilane and hexamethyldisilazane with N-methylamides of N′-organosulfonyl-2-amino acids (1a–e), the derivatives of N-mesylglycine (a), N-tosylglycine (b), N-nosylglycine (c), N-nosylalanine (d) and N-nosylleucine (e), affords new type of silacyclanes, 1-organosulfonyl-2-sila-5-piperazinones 2a–e. The presence of very labile Si–N bonds in compounds 2 can be utilised in a variety of synthetic applications. The hydrolysis of 2a–e yields disiloxanes 3a–e, which can be subsequently transformed into fluorosilanes, such as 4a, by the reaction with boron trifluoride. Ring-opening reactions of piperazinones 2b with 1-chloromethyl-2-pyrrolidone and acetyl bromide lead to previously unknown silyloxonium chloride 6b and silyloxonium bromide 8b, respectively, containing fragments of 2-amino acids as C,O-chelate ligands.Crystal structures of N-methylamide 1b, piperazinones 2a, d, e, disiloxanes 3c, e, fluorosilane 4a, silyloxonium chloride 6b and silyloxonium bromide 8b have been determined by X-ray diffraction study. The silicon atom in piperazinones and disiloxanes is tetracoordinated while compounds 4a, 6b and 8b contain pentacoordinated Si atoms.

Graphical abstractIn this paper we describe the isolation of new silacyclanes, 1-organosulfonyl-2-sila-5-piperazinones (2). The disiloxanes (3), fluorosilane (4) and silyloxonium ions (6,8) have been subsequently prepared from 2. The X-ray structures of nine tetra- and pentacoordinate silicon compounds are also reported.Figure optionsDownload full-size imageDownload as PowerPoint slide