15876-31-0Relevant academic research and scientific papers
Experimental studies of the anomeric effect. Part III. Rotameric preferences about the exo-cyclic c2-x bond in equatorial and axial 2-methoxy-and 2-methylamino-tetrahydropyrans
Booth, Harold,Dixon, J. Mark,Khedhair, Khedhair A.,Readshaw, Simon A.
, p. 1625 - 1652 (2007/10/02)
Values of3 J(CC), 3J(CH), 4J(CH) and 3J(HH), supported by n.O.enhancements, in nmr spectra of 2-methoxy- and 2-methyl-amino-tetrahydropyrans, point to a very strong preference for rotamers in which an exo-cyclic heteroatom lone pair is antiperiplanar to the endo-cyclic C2-O bond ("endo-anomeric effect").
On the Mechanism of Base-Induced Gas-Phase Elimination Reactions of Ethers
Koning, Leo J. de,Nibbering, Nico M. M.
, p. 1715 - 1722 (2007/10/02)
For the base-induced gas-phase elimination reactions of diethyl ether and cis- and trans-1-tert-butyl-4-methoxy-cyclohexane the kinetic isotope and leaving group effects have been determined as functions of the base strength using the method of Fourier transform ion cyclotron resonance mass spectrometry.The results are interpreted in terms of a variable E2 transition-state structure.Increasing the base strength causes the transition state to shift toward the carbanion or E1cb region of the E2 spectrum, which is also a general phenomenon in the condensed phase.Moreover, it appears that the elimination reactions most readily proceed via a transition state in which the β hydrogen and leaving group are periplanar.If the substrate does not easily allow such a relationship, the transition state is found to shift toward the carbenium ion or E1 region of the E2 spectrum where the geometric restrictions of the substrate are less perceptible.The concept of syn/anti dichotomy is used to explain the formation of tree and solvated alkoxide anions in the reactions induced by OH-.Anti elimination is believed to result in the formation of free alkoxide.Syn elimination, which takes advantage of the electrostatic interaction between the base and leaving group, is held responsible for the formation of solvated alkoxide.The importance of base/leaving group association in the transition state of the syn elimination is demonstrated by the low yield of solvated alkoxide in the reaction of OH-, solvated by a dimethylamine molecule, with diethyl ether.Finally, it seems that the selectivity of gas-phase elimination reactions is determined by not only the relative heights of the intrinsic reaction barriers, but also the relative stabilities of the ion/molecule complexes preceding the reaction barriers.
TRIMETHYLSILYL TRIFLATE IN ORGANIC SYNTHESIS
Noyori, R.,Murata, S.,Suzuki, M.
, p. 3899 - 3910 (2007/10/02)
Trimethylsilyl triflate is a powerful silylating agent for organic compounds and acts as a catalyst which accelerates a variety of nucleophilic reactions in aprotic media.The reactions proceed via one-center, electrophilic coordination of the silyl group to hetero functional groups and exhibit unique selectivities.
13C Nuclear Magnetic Resonance Spectra of Methoxycyclohexane Derivatives. Rotamer Populations about C-OMe Bonds as indicated by 13C Chemical Shifts of Methoxy- and Ring-carbons and 3JC,H Coupling Constants
Haines, Alan H.,Shandiz, Mohammad Seyedi
, p. 1671 - 1678 (2007/10/02)
Methoxy 13C chemical shifts in methoxycyclohexane derivatives may be rationalized in terms of rotamer populations about the C-OMe bond and δ1-effects caused by steric interaction of the methoxy-group with substituents at the neighbouring 2- and 6-positions.Information on rotamer populations is obtained also from the 13C chemical shifts of C-2 and C-6, and from the three-bond coupling between the proton at C-1 and the methoxy-carbon atom.
