Highly Selective One-Pot Synthesis of Polysubstituted Isoflavanes using Styryl Ethers and Electron-Withdrawing ortho -Quinone Methides Generated in Situ
A highly selective one-pot synthesis of polysubstituted isoflavanes has been developed. The reaction proceeds through the cycloaddition of methyl styryl ethers, derived from phenylacetaldehyde dimethyl acetals under acidic conditions, with electron-withdrawing ortho -quinone methides generated in situ. When phenylacetaldehyde dimethyl acetals were reacted with salicylaldehydes, the reaction proceeded smoothly to afford the corresponding isoflavanes stereoselectively in high yields and with excellent regioselectivities. The present reaction provides versatile access to functionalized isoflavanes, and constitutes a useful tool for the synthesis of biologically active molecules.
Hypoiodous acid-catalyzed regioselective geminal addition of methanol to vinylarenes: synthesis of anti-Markovnikov methyl acetals
A novel metal-free, catalytic geminal dimethoxylation of vinylarenes based on in situ generated HOI species from iodide salt and oxone is reported. The preliminary mechanistic investigations suggest that the key factor for achieving the anti-Markovnikov regioselectivity is the semipinacol rearrangement of an iodo functionalized intermediate, which is confirmed by an isotope labeling experiment. In addition, the reaction involves the de-iodination of a co-iodo intermediate via its oxidation to hypervalent iodine species rather than a common iodide abstraction by electrophiles. The HRESI-MS studies support the conversion of monovalent iodine containing intermediates to trivalent iodine intermediates during the catalytic conversion of aromatic alkenes into the corresponding terminal acetals.
A generalized approach for iron catalyzed chemo- and regioselective formation of anti-Markovnikov acetals from styrene derivatives
Fe(BF4)2·6H2O in the presence of pyridine-2,6-dicarboxylic acid and PhI(OAc)2 can efficiently catalyze the formation of chemoselective dialkyl acetals from styrene derivatives with anti-Markovnikov regioselectivity in good to high yields under mild and benign reaction conditions.
Chowdhury, Abhishek Dutta,Lahiri, Goutam Kumar
supporting information; experimental part
p. 3448 - 3450
(2012/05/20)
Effective Au(III)-CuCl2-catalyzed addition of alcohols to alkenes
Alkenes can be activated by Au(III) catalysts, and the effective addition of alcohols to alkenes can be carried out under mild conditions with Au(III), provided that catalytic amounts of CuCl2 are added, which significantly stabilize the cationic Au(III). The Royal Society of Chemistry.
Zhang, Xin,Corma, Avelino
p. 3080 - 3082
(2008/02/10)
Pd(II)-catalyzed conversion of styrene derivatives to acetals: Impact of (-)-sparteine on regioselectivity
Pd[(-)-sparteine]Cl2 catalyzes the formation of dialkyl acetals from styrene derivatives with Markovnikov regioselectivity. The substrate scope of this reaction has been investigated, and initial mechanistic studies indicate that the reaction proceeds through an enol ether intermediate and a Pd-hydride.
Balija, Amy M.,Stowers, Kara J.,Schultz, Mitchell J.,Sigman, Matthew S.
p. 1121 - 1124
(2007/10/03)
ELECTROOXIDATIVE REARRANGEMENT OF CONJUGATED ARYLOLEFINS TO ARYLACETALDEHYDE DIMETHYL ACETALS
Electrochemical oxidation of conjugated arylolefins 1 in trimethyl orthoformate containing iodine gave arylacetaldehyde dimethyl acetals 2 in high yields.
Substituent and Temperature Effects on the Reactions of Benzylchlorocarbene with Alcohol
The insertion reaction of the para-substituted benzylchlorocarbenes with methanol shows a second-order dependence in methanol, but only a first-order dependence in ethylene glycol.The results are consistent with a mechanism whereby the carbene inserts into the O-H bond of the alcohol dimer or oligomer by electrophilic attack of the carbene on the oxigenone pair to produce a reversibly formed ylide intermediate.The effects of the substituents indicate that electron-releasing group favours rearrangement while electron-withdrawing group facilitates insertion.Photolysis of halogenodiazirines in methanol at low temperatures give rise to V-shaped Arrhenius behaviour and the importance of N2 in influencing the reactivity of the singlet halogenocarbene in the matrix is demonstrated.
Liu, Michael T. H.,Subramanian, Ramasamy
p. 1233 - 1240
(2007/10/02)
Electroorganic Chemistry. 59. Electroreductive Synthesis of Oximes from Nitro Olefins