Organosubstituierte 1,6‐Dioxa‐2‐sila‐5‐bora‐3‐cycloalkene – Herstellung und Charakterisierung

Organosubstituted 1,6‐Dioxa‐2‐sila‐5‐bora‐3‐cycloalkenes – Preparation and Characterisation 1 ) The cis ‐alkenes ROSi(CH 3 ) 2 C(R) C(C 2 H 5 )B(C 2 H 5 )OR (R CH 3 : 11 ; C 2 H 5 : 12 ; C 6 H 5 : 13 ) are prepared from CH 3 NSI[CH 3 ) 2 C(R)C(C 2 H 5 )BC 2 H 5 [R CH 3 : A ; R C(CH 3 ) CH 2 : B ] with the monohydroxy compounds ROH (R CH 3 , C 2 H 5 , C 6 H 5 ). A or B react with aliphatic dihydroxy compounds HOR′OH [R′ CH 2 CH 2 : 1 ; CH(CH 3 )CH 2 : 2 ; CH(CH 3 )CH(CH 3 ): 3 ; C(CH 3 ) 2 C(CH 3 ) 2 : 4 ; (CH 2 ) 3 : 5 ; (CH 2 ) 4 : 6 ] to give 8‐, 9‐, and 10‐membered ring compounds OSi(CH 3 ) 2 C(R) C(C 2 H 5 )OR′ [ 15a,b, 16/16′ , meso/rac ‐ 17a , D ‐ 17a,b, 18, 19, (20) n ]. A is initially cleaved at the SiN bond with formation of 14 Compound 15a crystallises as the 16‐membered ( 15a ) 2 [X‐ray structure analysis). The aromatic dihydroxy compounds catechol ( 7 ), resorcinol ( 8 ), 2,3‐dihydroxynaphthalene ( 9 ), 1, 8‐dihydroxynaphthalene ( 10 ) react with A to form 21 to 24 , but mainly by protolytic BC vinyl fission to give the 2,5‐dihydro‐1,2,3‐dioxaboroles (e.g. 7f 1 , 9f 1 , 10f 1 ) and the acyclic boron‐free compounds 7f ′ 3 , 9f 3 , 10f 3 . The MS and NMR ( 1 H, 11 B, 13 C, 29 Si) data of the new compounds are discussed.