| Attributs | Valeurs |
|---|
| type
| |
| Is Part Of
| |
| Subject
| |
| Title
| - β-Silylcarbenes from Isolable Diazosilanes
|
| has manifestation of work
| |
| related by
| |
| Author
| |
| Abstract
| - Manganese dioxide oxidation of the hydrazone derivative of tert-butyldimethylsilyl acetophenonegave 2-tert-butyldimethylsilyl-1-phenyldiazoethane (17) an isolable diazocompound. Thermal andRh(II)-catalyzed decomposition of diazosilane 17 in cyclohexane led to 1-tert-butyldimethylsilyl-1-phenylethylene (19) as the major product. The formation of alkene 19 presumably involves (tert-butyldimethylsilyl)methylphenylcarbene (21), which undergoes preferential 1,2-silyl migration asopposed to 1,2-hydrogen migration. Thermal decomposition of 17 in cyclohexane under oxygen gavesubstantial amounts of tert-butyldimethylsilyl acetophenone, presumably by reaction of theintermediate carbene with oxygen. Thermal decomposition of 17 in methanol led to alkene 19 and2-tert-butyldimethylsilyl-1-methoxy-1-phenylethane (22) as major products, along with a significantamount of trans-1-tert-butyldimethylsilyl-2-phenylethylene (20). Kinetic studies indicate that theseproducts are not derived from acid-catalyzed decomposition of the diazocompound 17. Formationof the methyl ether product 22 suggests the involvement of a β-silyl carbocation intermediate, andsolvent isotope effect studies indicate that this cation is at least partially derived from protonationof diazocompound 17 by neutral methanol. Photochemical decomposition of 17 in methanol producedthe alkene 19 (97%) along with a small amount (2.4%) of the methyl ether 22. Capture of aphotochemically generated carbene 21 by methanol is the proposed origin of this minor product.Geometry optimization of trimethylsilylmethylphenylcarbene (8) and carbene 21 at the HF/6-31G*computational level led to a conformation consistent with a hyperconjugative interaction betweenthe vacant p-orbital of these carbenes and the adjacent C−Si bond. Carbenes 8 and 21 are notenergy minima at the B3LYP/6-31G* level, where they rearrange to alkenes without barrier viasilyl migration. These theoretical findings contrast with the proposed trapping of carbene 21 bymethanol and oxygen.
|
| article type
| |
| is part of this journal
| |
