135366-65-3Relevant academic research and scientific papers
Dimethyldioxirane Oxidation of Titanium Enolates: Diastereoselective α-Hydroxylations
Adam, Waldemar,Mueller, Michael,Prechtl, Frank
, p. 2358 - 2364 (1994)
The oxidation of titanium enolates, derived from a transmetalation of the corresponding lithium enolates with (i-PrO)3TiCl, (Et2N)3TiCl, or Cp2TiCl2, by dimethyldioxirane has been investigated.Furthermore, the diastereoselective hydroxylation of the chiral metal enolates, e.g., derived from camphor (1f), menthone (1g), flavanone (1h), and 2-benzylcyclopentanone (1i), by dimethyldioxirane has been examined.The diastereoselectivity of the oxygen transfer strongly depends on the metal partner coordinated to the enolate.The titanium enolates 4 resulted in much higher diastereoselectivities (up to 96percent de) than the corresponding sodium enolates 5 and at least as high if not higher than the silyl enol ethers 6.Moreover, the aldol reaction of ester-derived sodium enolates with acetone, the unavoidable medium for dimethyldioxirane, could be totally suppressed by the use of the chlorotitanocene enolates 4.Thus, the oxidation of chiral titanium enolates by dimethyldioxirane represents a general, convenient, effective, and chemo- and diastereoselective synthesis of α-hydroxy carbonyl compounds.
The thionophosphate-thiolophosphate photoisomerization proceeds predominantly through a non-chain radical pathway. Synthetically viable benzylation of tetrahydrofuran, propan-2-ol and olefins
Yadav, Veejendra K.,Balamurugan, Rengarajan,Parvez, Masood,Yamdagni, Raghav
, p. 323 - 332 (2007/10/03)
The photoirradiation of thionophosphates, ROP(S)(OEt)2, derived from benzyl and vinylogously benzyl alcohols in CH3CN, with a Hanovia medium-pressure mercury lamp in a quartz vessel leads to the formation of the corresponding thiolophosphates, RSP(O)(OEt)2, through a non-chain radical pathway. This behavior of thionophosphates is unlike that of the related phosphates, which react through ionic dissociation-recombination processes. When the irradiation is conducted in solvents such as PriOH, THF and toluene, benzylation of these solvents takes place in synthetically respectable yields. Irradiation of thionophosphates in CH3CN leads to a convenient allylic benzylation of olefins.
Highly Efficient Hydroxylation of Carbonyl Compounds with Dimethyldioxirane
Adam, Waldemar,Prechtl, Frank
, p. 2369 - 2372 (2007/10/02)
The enolates and/or enols of ketones, esters, β-diketones, β-oxo esters, and β-oxolactones were transformed by dimethyldioxirane (isolated in acetone solution or generated in situ) into their α-hydroxy compounds in good to excellent yields.The direct hydroxylation of the enols was significantly enhanced by the use of fluoride ion.For the enolate of camphor the exo/endo diastereoselectivity depended significantly on the metal ligand; the highest exo/endo ratio (93:7) was observed for the enol trimethylsilyl ether of camphor.Key Words: Dimethyldioxirane / Enolates / Hydroxylation / α-Hydroxy carbonyl compounds / Enol silyl ethers
Carbenes in a Rigid Matrix. Substituent Effects on the Temperature Dependence of α-Carbonylcarbene Reactions
Tomioka, Hideo,Okuno, Hiroshi,Izawa, Yasuji
, p. 1636 - 1641 (2007/10/02)
The temperature dependence of methoxycarbonyl- (1a and b) and benzoyl-carbenes (2a and b) reactions in alcohols has been examined in order to elucidate the scope and limitation of low temperature photolysis as a tool for detecting triplet carbenes.The results reveal that the method cannot be applied to all carbenes but gives important information on the reactivity and/or multiplicity of ground-state carbenes.Low-temperature photolysis of PhCN2CO2Me in an ethanol matrix, for example, resulted in a dramatic increase in C-H insertion products, probably derived from the triplet (1a) via an abstraction-recombination mechanism, at the expense of the singlet product, i.e. the O-H insertion compound, which was shown to be the main product of photolysis at ambient temperature.In marked contrast, (1b) generated in a propan-2-ol matrix at -196 deg C did not result in a major increase in the C-H insertion product.Similar and more contrasting substituent effects on the temperature dependence were observed in the benzoylcarbene system (2).Thus, the Wolff rearrangement of (2a) was almost completely supressed in a rigid matrix at -196 deg C, whereas that of (2b) was not appreciably supressed even at -196 deg C.These differences were explained by considering the effects of the substituent on the ground-state multiplicity of carbene and/or on the relation of the activation energy differences of the singlet and triplet reactions with energy differences between two states.
Unambiguous Proof for Alcoxycarbonyl-group Migration in Wagner-Meerwein Rearrangements
Berner, Daniel,Dahn, Hans,Vogel, Pierre
, p. 2538 - 2553 (2007/10/02)
In HSO3F/SO2ClF the β-hydroxy esters Ph-CHOH-CMe2-COOR (1, R=Me, Et) are doubly protonated, then transformed into the fluorosulfates 7 and (partly) into the fluorides 8.At -15 deg C, both 7 and 8 undergo a rearrangement, forming derivatives of Me2C=C(Ph)C
