64698-20-0Relevant academic research and scientific papers
A facile microwave-assisted Diels-Alder reaction of vinylboronates
Sarotti, Ariel M.,Pisano, Pablo L.,Pellegrinet, Silvina C.
supporting information; experimental part, p. 5069 - 5073 (2010/12/25)
The Diels-Alder reaction of vinylboronates can be easily performed using microwave irradiation giving excellent yields of the cycloadducts. Pinacol vinylboronate was the reagent of choice due to its stability towards hydrolysis, operational simplicity and yields of Diels-Alder products. To the best of our knowledge, this is the first example of microwave-assisted Diels-Alder reaction of boron-substituted dienophiles. Subsequent in situ oxidation of the cycloadducts with alkaline hydrogen peroxide afforded the alcohols efficiently.
Regioselective SN2 opening of vinylic epoxides with trialkylzincates and trialkylaluminates
Equey, Olivier,Vrancken, Emmanuel,Alexakis, Alexandre
, p. 2151 - 2159 (2007/10/03)
The use of trialkylorganozincates and tetraalkylaluminates allows regioselective SN2 nucleophilic opening of vinylic epoxides. The reaction occurs with an anti-substitution pattern and can be applied to a wide range of substrates. We also show that the solvent and the structure of the epoxide have an influence on the substitution products' ratio. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Asymmetric synthesis of cyclic alkenes via cyclization of enantioenriched allylsilanes
Suginome,Iwanami,Yamamoto,Ito
, p. 1042 - 1045 (2007/10/03)
Intramolecular cyclizations of optically active allylsilanes bearing electrophilic functional groups on their α-alkyl side chains were examined. The allylsilanes having aldehyde and enone functional groups underwent the intramolecular cyclizations in the presence of Lewis acid catalysts to give 6- and 7-membered cycloalkenes with high stereoselectivity in good yields. Reactions of the allylsilanes having α-hydroxyalkyl chain with aldehydes provided 6- and 7-membered oxacycloalk-4-enes stereoselectively in good yields. Use of highly enantioenriched allylsilanes furnished enantioenriched cyclic alkenes with almost perfect chirality transfer from the allylsilanes.
Regioselective SN2 opening of α,β-ethylenic epoxides by RLi-BF3 combination
Alexakis, Alexandre,Vrancken, Emmanuel,Mangeney, Pierre,Chemla, Fabrice
, p. 3352 - 3353 (2007/10/03)
Organolithium reagents effect a regioselective SN2 nucleophilic cleavage of α,β-ethylenic epoxides only when BF3·Et2O is added. The reaction works with a variety of RLi reagents and with cyclic as well as acyclic epoxides. The Royal Society of Chemistry 2000.
Tuning of vinylborane dienophilicity. Optimization of reactivity, regioselectivity, endo stereoselectivity, and reagent stability
Singleton, Daniel A.,Martinez, Jose P.,Watson, Jose V.,Ndip, Grace M.
, p. 5831 - 5838 (2007/10/02)
Simple syntheses of some vinylboranes are reported, and their properties in Diels-Alder reactions are compared. Vinyl-3,6-dimethylborepane was the most stable simple vinylborane examined, and appears to be indefinitely stable at 25°C. Surprisingly, trivinylborane is the most reactive, and reacts about 18 times faster than the vinyldialkylboranes with cyclopentadiene. Vinyl-9-BBN is the most regioselective dienophile, in keeping with principally steric control of regioselectivity in Diels-Alder reactions of vinylboranes. All the dienophiles display high endo-stereoselectivity with piperylene, but vinyl-3,6-dimethylborepane displays significantly improved stereoselectivity with cyclopentadiene. In general, by choice of alkyl-substituents on boron, the reactivity, regioselectivity, endo-stereo selectivity, and stability of vinylboranes can be optimized.
A short and efficient synthesis of the C-3 to C-10 portion of the maytansinoids
Hodgson,Parsons,Stones
, p. 4133 - 4142 (2007/10/02)
The cyclic carbamate (3), a key intermediate in our projected synthesis of trenudine (2), has been synthesised from 3,4-epoxycyclohexene (4) by ozonolytic cleavage of the cyclopentene (9) as a key step.
A PHOTOCHEMICAL SYNTHESIS OF βγ-EPOXYCYCLOHEXANONES
Carless, Howard A. J.,Fekarurhobo, G. K.
, p. 107 - 110 (2007/10/02)
The βγ-epoxycyclohexanones (1), (9) and (10) have been prepared by photolysis of the pyruvate esters derived from the corresponding epoxyalcohols.
Steric vs. Stereoelectronic Effects in Carbocation Reactions of the 2-Bicyclononyl System
Friedrich, Edwin C.,Biresaw, Girma,Saleh, Mahmoud A.
, p. 1435 - 1439 (2007/10/02)
An investigation of anti-9-methyl substituent effects upon the kinetics and products of hydrolysis of the cis-ring-fused endo- and exo-2-bicyclononyl 3,5-dinitrobenzoates in 80percent aqueous acetone has been carried out.In the exo system, the anti-9-methyl substituent produced only a small rate-accelerating effect of 1.8 at 80 deg C.However, for the endo system acceleration by a factor of 4.7 was observed.In neither system did the anti-9-methyl substituent affect the exo:endo product ratio.With the anti-6-methyl-2-bicyclohexyl 3,5-dinitrobenzoates, which were studied for comparison, the anti-6-methyl substituent exhibited an identical rate-accelerating effect of 8.3 in both the endo and the exo isomers.Also, with both isomers an identical exo:endo product ratio was observed.On the basis of these results, it is proposed that the stereoselectivities observed in product formation in the 2-bicyclononyl system are not due primarily to electronic factors but result mainly from steric effects upon structurally different, noninterconverting intermediates with bisected delocalization.
CYCLOHEXENOL ANNULATION VIA THE ALKOXY-ACCELERATED REARRANGEMENT OF VINYLCYCLOBUTANES
Danheiser, Rick L.,Martinez-Davila, Carlos,Sard, Howard
, p. 3943 - 3950 (2007/10/02)
The lithium and potassium salts of 2-vinylcyclobutanols undergo vinylcyclobutane rearrangement at 25-70 gradC, providing an efficient method for the synthesis of 3-cyclohexenol derivatives. 2-Vinylcyclobutanones are prepared from α,β-unsaturated carbonyl
