Beschreibung:
<jats:title>Abstract</jats:title><jats:p>The lithium salts of the Me<jats:sub>3</jats:sub>Si‐ as well as Me<jats:sub>3</jats:sub>Si‐ and Me<jats:sub>2</jats:sub>SiF‐substituted Cyclotrisilazanes <jats:bold>I</jats:bold> and <jats:bold>II</jats:bold> react with <jats:italic>tert</jats:italic>‐butylacylchloride under ring contraction and formation of the cyclodisilazane‐silylester, Me<jats:sub>3</jats:sub>SiN(SiMe<jats:sub>2</jats:sub>–N)<jats:sub>2</jats:sub>SiMe<jats:sub>2</jats:sub>–O–CO–CMe<jats:sub>3</jats:sub> (<jats:bold>1</jats:bold>). The lithium salt of the fluorodi‐methylsilyl‐substituted cyclotrisilazan <jats:bold>III</jats:bold> forms with benzoylchloride primarily in the analogous reaction the carboxy‐silyl‐amide, Me<jats:sub>2</jats:sub>SiF(N–SiMe<jats:sub>2</jats:sub>)<jats:sub>2</jats:sub>SiMe<jats:sub>2</jats:sub>–NH–CO–C<jats:sub>6</jats:sub>H<jats:sub>5</jats:sub><jats:sup>+</jats:sup> (<jats:bold>2</jats:bold>), which can be converted with <jats:bold>III</jats:bold> and benzoylchloride into the cyclodisilazane‐silylester, Me<jats:sub>2</jats:sub>SiF(NSiMe<jats:sub>2</jats:sub>)<jats:sub>2</jats:sub>SiMe<jats:sub>2</jats:sub>–O–CO–C<jats:sub>6</jats:sub>H<jats:sub>5</jats:sub>, (<jats:bold>3</jats:bold>). A silylester substituted six‐membered disila‐oxadiazine (<jats:bold>4</jats:bold>) is the result of the reaction of the lithiated cyclotrisilazane, (Me<jats:sub>2</jats:sub>SiNH)<jats:sub>2</jats:sub>, (Me<jats:sub>2</jats:sub>SiNLi) with <jats:italic>tert</jats:italic>‐butyl‐acylchloride. The reaction includes anionic ring contraction and can be rationilized by a process analogous to keto‐enol‐tautomerism. Dilithiated octamethyl‐cyclotetrasilazane, (Me<jats:sub>2</jats:sub>SiNHMe<jats:sub>2</jats:sub>SiNLi)<jats:sub>2</jats:sub>, reacts with <jats:italic>tert</jats:italic>‐butyl‐acylchloride or benzoylchloride in a molar ratio 1:2 to yield symmetrically acylestersubstituted cyclodisilazanes, (RCO–O–SiMe<jats:sub>2</jats:sub>–NSiMe<jats:sub>2</jats:sub>)<jats:sub>2</jats:sub>, R = C<jats:sub>6</jats:sub>H<jats:sub>5</jats:sub> (<jats:bold>5</jats:bold>), CMe<jats:sub>3</jats:sub> (<jats:bold>6</jats:bold>). The reaction mechanisms are discussed and the crystal structures of <jats:bold>2</jats:bold> and <jats:bold>6</jats:bold> are reported.</jats:p>