title: Synthesis of 2,2,5,5-tetrasubstituted 1,4-dioxa-2,5-disilacyclohexanes via organotin(IV)-catalyzed transesterification of (acetoxymethyl)alkoxysilanes.
abstract: (Acetoxymethyl)silanes 2, 7a-c, and 10a-c with at least one alkoxy group, of the general formula (AcOCH2 )Si(OR)3-n(CH3)n (R: Me, Et, iPr; n=0, 1, 2), were synthesized from the corresponding (chloromethyl)silanes 1, 6a-c, and 9a-c by treatment with potassium acetate under phase-transfer-catalysis conditions. These compounds were found to provide 2,2,5,5-organo-substituted 1,4-dioxa-2,5-disilacyclohexanes 3, 8a-c, and 11a-c if treated with organotin(IV) catalysts such as dioctyltin oxide. The reaction proceeds through transesterification of the acetoxy and alkoxy units followed by ring-closure to form a dimeric six-membered ring. The corresponding alkyl acetates are formed as the reaction by-products. With these mild conditions, the method overcomes the drawbacks of previously reported synthetic routes to furnish 2,2,5,5-tetramethyl-1,4-dioxa-2,5-disilacyclohexane (3) and even allows the synthesis of 1,4-dioxa-2,5-disilacyclohexanes bearing hydrolytically labile alkoxy substituents at the silicon atom in good yields and high purity. These new materials were fully characterized by NMR spectroscopy, elemental analysis, mass spectrometry, and X-ray analysis (trans-8a).
authors: Wacker-Lehrstuhl für Makromolekulare Chemie, Institut für Siliciumchemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
authors: Sascha A
authors: SA
authors: Erhardt
authors: Florian
authors: F
authors: Hoffmann
authors: Jürgen O
authors: JO
authors: Daiss
authors: Jürgen
authors: J
authors: Stohrer
authors: Eberhardt
authors: E
authors: Herdtweck
authors: Bernhard
authors: B
authors: Rieger