18388-07-3Relevant academic research and scientific papers
Synthesis of Highly Oxygenated Carbocycles by Stereoselective Coupling of Alkynes to 1,3- and 1,4-Dicarbonyl Systems
Kier, Matthew J.,Leon, Robert M.,O'Rourke, Natasha F.,Rheingold, Arnold L.,Micalizio, Glenn C.
supporting information, p. 12374 - 12377 (2017/09/23)
Densely substituted and highly oxygenated carbocycles are challenging targets for synthesis. In particular, those possessing numerous contiguous, fully substituted carbon atoms (i.e., tertiary alcohols and quaternary centers) are often not accessible in a direct fashion, necessitating the strategic decoupling of ring-formation from the establishment of functionality about the system. Here, we describe an approach to the construction of highly oxygenated mono-, di-, and polycyclic carbocycles from the reaction of disubstituted alkynes with β- or γ-dicarbonyl systems. These processes embrace a variant of metallacycle-mediated annulation chemistry where initial alkyne-carbonyl coupling is followed by a second, now intramolecular, stereoselective C-C bond-forming event. In addition to revealing the basic reactivity pattern in intermolecular settings, we demonstrate that this class of reactivity is quite powerful in a fully intramolecular context and, when terminated by a stereoselective oxidation process, can be used to generate polycyclic systems containing a fully substituted and highly oxygenated five-membered ring.
Unique σ-bond metathesis of silylalkynes promoted by an ansa-dimethylsilyl and oxo-bridged uranium metallocene
Wang, Jiaxi,Gurevich, Ylia,Botoshansky, Mark,Eisen, Moris S.
, p. 9350 - 9351 (2007/10/03)
The tetrachloride salt of uranium reacts with 1 equiv of the lithium ligand Li2[(C5Me4)2SiMe2] in DME to form the complex [η5-(C5Me4)2SiMe2]UCl2·2LiCl·2DME (1), which undergoes a rapid hydrolysis in toluene to yield the dimeric bridged monochloride, monooxide complex [{[η5-(C5Me4)2SiMe2]UCl}2(μ-O)(μ-Cl)?Li?1/2DME]2 (2). Metathesis of 2 with BuLi in DME gives the mono-bridged dibutyl complex {[η5-(C5Me4)2SiMe2]UBu}2(μ-O) (3). Complex 2 was characterized by solid-state X-ray analysis. Complex 3 was found to be an active catalyst for the disproportionation metathesis of TMSC≡CH (TMS = SiMe3) and the cross-metathesis of TMSC≡CH or TMSC≡CTMS with various terminal alkynes. The metathesis of TMSC≡CH gives TMSC≡CTMS and HC≡CH, whereas the cross-metathesis of TMSC≡CH or TMSC≡CTMS with terminal alkynes (RC≡CH) yields TMSC≡CTMS, TMSC≡CR, and HC≡CH. In addition, TMSC≡CCH3 also was found to react with tBuC≡CH, yielding TMSC≡CBut and CH3C≡CH. A plausible mechanism for the catalytic process is presented. Copyright
Synthesis of α-iodo-α,β-unsaturated ketones by the reaction of α- silyl-α,β-unsaturated ketones with ICl or ICIl-AlCl3
Alimardanov, Asaf,Negishi, Ei-ichi
, p. 3839 - 3842 (2007/10/03)
Treatment of α-silyl-α,β-unsaturated enones, readily preparable as regio- and stereodefined compounds in high yields, with either 2 equiv, of ICl or one equiv, each of ICl and AlCl3 provides the corresponding α-iodo- α,β-unsaturated enones in h
A new route to α,β-unsaturated aldehydes using the condensation of trimethylsilyl β-trimethylsilyl enol ethers with aldehydes
Duhamel, Lucette
, p. 7745 - 7748 (2007/10/02)
β-Trimethylsilyl enol ethers 1 (Z) obtained from β-bromoenolethers 2 were condensed with aliphatic and aromatic aldehydes in the presence of a catalytic quantity of trimethylsilyl triflate leading to ethylenic aldehydes 3 (E) with good yields (79-90%).
Acylsilenes (3-Oxo-1-sila-1-propenes) from Acyl(disilanyl)carbenes
Schneider, Klaus,Daucher, Birgit,Fronda, Antonio,Maas, Gerhard
, p. 589 - 594 (2007/10/02)
UV photolysis of diazo(disilanyl)methyl ketones 2 in benzene generates acyl(disilanyl)carbenes 3, which rearrange to 3-oxo-1-sila-1-propenes 4.The latter compounds are reactive intermediates which either cyclize to 1-oxa-2-sila-3-cyclobutenes 5 or form th
Gas-Phase Kinetics of Pyrolysis of 3,3-Dimethylcyclopropene and Its 1-Trimethylsilyl Derivative The Effect of Silyl Substitution on Cyclopropene Isomerisation
Walsh, Robin,Untiedt, Sven,Stohlmeier, Michael,Meijere, Armin de
, p. 637 - 642 (2007/10/02)
The gas-phase pyrolysis of 3,3-dimethylcyclopropene (1) in the temperature range of 185-225 deg C gives 3-methyl-1-butyne (2) (91percent) and isoprene (3) (9percent).The gas-phase pyrolysis of 3,3-dimethyl-1-trimethylsilylcyclopropene (4) in the temperature range of 195-235 deg C gives 3-methyl-1-trimethylsilyl-1-butyne (5) (99percent) and trans-3-methyl-1-trimethylsilyl-1,3-butadiene (6) (1percent).Both rearrangements are homogeneous, first-order, unimolecular reactions with the following pressure-independent Arrhenius parameters. Rather surprisingly, the trimethylsilyl group deactivates cyclopropene with respect to its isomerisation.Possible mechanisms are discussed. - Keywords: Cyclopropene, 3,3-dimethyl-1-trimethylsilyl-/ Cyclopropene, isomerisation/ Gas-phase kinetics/ Ring-opening of 3,3-dimethylcyclopropene/ Vinylcarbene intermediates
Cyclic Isomers and Cyclodimers of 3-Oxo-1-silaprop-1-enes
Maas, Gerhard,Schneider, Klaus,Ando, Wataru
, p. 72 - 74 (2007/10/02)
3-Oxo-1-silaprop-1-enes, when generated by photochemical decomposition of α-diazo-α-silyl carbonyl compounds, cyclize to 1-oxa-2-silacyclobut-3-enes provided that the substituent at C-3 is sterically demanding; otherwise, the head-to-tail cyclodimers (1,5,dioxa-2,6-disilacyclo-octa-3,7-dienes) are obtained.
The Chemistry of Allene Cation Radicals Probed by the Use of Theoretical and Electron-Transfer Photochemical Methods
Haddaway, Keith,Somekawa, Kenichi,Fleming, Paul,Tossell, John A.,Mariano, Patrick S.
, p. 4239 - 4253 (2007/10/02)
Theoretical and photochemical methods have been used to probe the structures, electronic distributions, and solution-phase chemical properties of allene cation radicals.Results of SCF-level (UHF) calculations show that the linear-45 deg-twisted structure
A Simple, New Preparation of α,α-Dimethylallyltrimethylsilane: a Useful Prenylation Reagent
Bennetau, Bernard,Pillot, Jean-Paul,Dunogues, Jacques,Calas, Raymond
, p. 1094 - 1095 (2007/10/02)
Starting from 3-methylbut-1-yn-3-ol, a short synthesis of α,α-dimethylallyltrimethylsilane (a selective prenylation reagent) has been achieved in 47percent overall yield; several other unsaturated organosilicon intermediates of wide potential utility in organic synthesis are also prepared.
