Jürgen Stohrer

Synthesis of 2,2,5,5‐Tetrasubstituted 1,4‐Dioxa‐2,5‐disilacyclohexanes via Organotin(IV)‐Catalyzed Transesterification of (Acetoxymethyl)alkoxysilanes

(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).