- B(C6F5)3-Catalyzed Diastereoselective Formal (4 + 1)-Cycloaddition of Vinylcyclopropanes and Et2SiH2
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A formal (4 + 1)-cycloaddition of vinylcyclopropanes and Et2SiH2 to afford 3,4-disubstituted silolanes is reported. The reaction sequence commences with the known B(C6F5)3-catalyzed alkene hydrosilylation with dihydrosilanes. Cleavage of the remaining Si-H bond in the hydrosilylation product assisted by B(C6F5)3 leads to formation of a cyclopropane-stabilized silylium ion. The activated cyclopropane ring is then opened by the in situ-generated borohydride accompanied by ring closure to the silolane. The diastereoselectivity is rationalized by a mechanistic model.
- Long, Peng-Wei,Oestreich, Martin
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- Cyclopentanone derivatives
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Cyclopentane derivatives of the formula: STR1 wherein R1 represents hydrogen or a carboxylic acyl group, and either (I) R2 represents a group of the formula: (wherein R3 and R4 represent hydrogen or alkyl, and R5 represents hydrogen, or alkyl, alkoxy, cycloalkyl or adamantyl, or R5 represents alkyl substituted by alkoxy, or by cycloalkyl or by adamantyl, or the group --CR3 R4 R5 together forms a cycloalkyl or adamantyl group), X represents trans-vinylene or ethylene and Y represents carbonyl or a group of the formula: STR2 wherein R6 represents hydrogen or alkyl, and R7 represents hydrogen or a carboxylic acyl group, or else (ii) R2 represents a group of the formula: (wherein A represents alkylene, Z represents a direct bond or oxygen or sulphur, and R8 represents an aryl or heterocyclyl group which may be substituted by one or more of halogen, alkyl, alkoxy and trihalomethyl), X in formula I represents ethylene or trans-vinylene and Y in formula I represents carbonyl or a group of formula III, or else (iii) R2 represents a group R8 and X and Y in formula I represent simultaneously ethylene and carbonyl, trans-vinylene and carbonyl, or ethylene and --CH(OR7)-- groups respectively. The compounds are new and possess pharmacological properties similar to those of prostaglandins.
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