Hydroboration. 86. Convenient conversion of aldehydes and ketones into the corresponding alkenes via hydroboration of their enamines. A remarkably simple synthesis of either (Z)- or (E)-alkenes
摘要:
Aldehydes and ketones are converted into the corresponding alkenes via hydroboration of their enamines. Hydroboration of aldehyde enamines by 9-borabicyclo[3.3.1]nonane (9-BBN), followed by methanolysis, affords the corresponding terminal alkenes in 75-90% yields. Unsaturated aldehyde enamines produce the corresponding dienes under these conditions. Enamines derived from substituted cyclic ketones and heterocyclic ketones are readily accommodated in this reaction to afford the corresponding alkenes in very good yields. The synthesis of pure (Z)- or (E)-alkenes is readily achieved from the same acyclic ketone enamine by modification of the hydroboration-elimination procedure: (A) hydroboration by 9-BBN followed by methanolysis or (B) hydroboration by borane methyl sulfide (BMS) followed by methanolysis and hydrogen peroxide oxidation. Mechanistic rationale is provided.
Vacuum flash pyrolysis (VFP) of malonyl peroxides: decarboxylation versus decarbonylation of the intermediary α-lactones
作者:Waldemar Adam、Carlos Cadiz、Francois Mazenod
DOI:10.1016/s0040-4039(01)90274-6
日期:1981.1
VacuumFlashPyrolysis (VFP) at ca. 450–500°C and ca. 0.1–0.3 Torr of the spirocyclic malonyl peroxides (2a,b) affords high yields of allenes (5a,b), while the simple malonyl peroxide (2c) leads to ketone (4), derived respectively from decarboxylation and decarbonylation of the intermediary α-lactones (3).
Homoallylic substitution reactions of lithium dialkyl cuprates with cyclopropylcarbinyl halides: mechanistic considerations
作者:Robert T. Hrubiec、Michael B. Smith
DOI:10.1016/s0040-4020(01)91792-2
日期:1984.1
kanes, , react to give good yields of the homoallylic substitution product, . Less reactive organocuprates react with to give mixtures of and the direct substitution product, . These results are consistent with a copper(I) radical intermediate which undergoes facile rearrangement prior to reductive coupling.
Treatment of secondary-alkyl Phenylselenides with various oxidants affords the corresponding trans-alkene highly selectively irrespective of the amount of oxidant, while in the case of the tellurium, analogues the doublebondgeometry of the product alkene depends markedly on the amount of oxidant, the trans-isomer being formed highly selectively with 1 equiv. oxidant and the proportion of the cis-isomer
High Yield of Liquid Range Olefins Obtained by Converting <i>i</i>-Propanol over Zeolite H-ZSM-5
作者:Uffe V. Mentzel、Saravanamurugan Shunmugavel、Sarah L. Hruby、Claus H. Christensen、Martin S. Holm
DOI:10.1021/ja907692t
日期:2009.11.25
Methanol, ethanol, and i-propanol were converted under methanol-to-gasoline (MTH)-like conditions (400 degrees C, 1-20 bar) over zeolite H-ZSM-5. For methanol and ethanol, the catalyst lifetimes and conversion capacities are comparable, but when i-propanol is used as the reactant, the catalyst lifetime is increased dramatically. In fact, the total conversion capacity (calculated as the total amount
1,2-Dialkylvinylsilanes from α-silyl epoxides via organolithium reagents
作者:Braulio Santiago、Carlos Lopez、John A. Soderquist
DOI:10.1016/0040-4039(91)80805-g
日期:1991.7
The reactions of cis-α-epoxysilanes (1) with an excess of alkyllithium reagents were found to cleanly provide 1,2-dialkylvinylsilanes (3). A model for this reductive alkylation is advanced which explains the role of substituents in determining the product stereochemistry.