Search

Oxygen-containing heterocyclic systems are important structures in organic chemistry because of their presence in many biologically active compounds. In this work, a Lewis acid-catalyzed cyclization of ethenetricarboxylate derivatives 1 with substituted propargyl alcohols to give methylenetetrahydrofurans was investigated. Reaction of 1 and gamma-silicon-substituted propargyl alcohols 4 with ZnBr2 at 80-110 degrees C led to (Z)-silicon-substituted products stereoselectively. Reaction of 1 and gamma-ester-substituted propargyl alcohol 7 in the presence of various Lewis acids gave ester-substituted methylenetetrahydrofurans stereoselectively. Interesting Lewis acid dependency on stereoselectivity for the reaction of 7 was found. Reaction of alpha-substituted propargyl alcohols also gave cyclized products.

Modification of hydrogen-terminated Si(1 1 1) surfaces by hydrosilylation of activated alkenes and further chemical transformation of the modified surfaces is reported. A Si(1 1 1)–H surface was reacted with activated alkenes such as acrylate esters, acrylonitrile, and maleic anhydride under mild conditions to give modified surfaces with terminal functional groups. A modified surface with a terminal ester group was reduced by LiAlH 4 to give a hydroxy-terminated surface, and the hydroxy-terminated surface was transformed to a bromo-terminated surface. XPS analysis revealed that the brominated surface ( Si(1 1 1)–CH 2 CH 2 CH 2 Br) had 32% coverage with the 3-bromopropyl group. Ester and amide formation reactions were carried out on hydroxy- and carboxy-terminated Si surfaces by reaction with tert -butoxycarbonyl glycine, glycine tert -butyl ester, 2,2,2-trifluoroethanol and 4-trifluoromethylbenzyl alcohol in the presence of carbodiimide. XPS characterization indicated that the esters and amide were successfully formed with coverage ranging from 16% to 58%. Coverage ratios of octadecyl ester modified surfaces were also estimated by combination of surface reduction and gas chromatography analysis to be 25–35%.

Oxygen-containing heterocyclic systems are important structures in organic chemistry because of their presence in many biologically active compounds. In this work, a Lewis acid-catalyzed cyclization of ethenetricarboxylate derivatives 1 with substituted propargyl alcohols to give methylenetetrahydrofurans was investigated. Reaction of 1 and γ-silicon-substituted propargyl alcohols 4 with ZnBr2 at 80−110 °C led to (Z)-silicon-substituted products stereoselectively. Reaction of 1 and γ-ester-substituted propargyl alcohol 7 in the presence of various Lewis acids gave ester-substituted methylenetetrahydrofurans stereoselectively. Interesting Lewis acid dependency on stereoselectivity for the reaction of 7 was found. Reaction of α-substituted propargyl alcohols also gave cyclized products.