18412-38-9Relevant articles and documents
Carbanion Rearrangements of ω-Phenyl-ω-(trimethylsilyl)alkyllithium Compounds: Intramolecular Reactions of Benzyltrimethylsilanes with a Carbon-Lithium Bond
Maercker, Adalbert,Stoetzel, Reinhard
, p. 1695 - 1706 (2007/10/02)
ω-Phenyl-ω-(trimethylsilyl)alkyllithium compounds show four out of five theoretically conceivable possibilities for intramolecular stabilization depending on the solvent and on the chain length n.While transmetalation of a methyl group at the silicon atom by a 1,(n+2) proton transfer is observed in any case, the intramolecular 1,n shift of the benzylic proton does only take place with n >/= 4.The main reaction, however for n = 3 and 4 only, is represented by the 1,n trimethylsilyl shift via a cyclic ate complex as an intermediate which partly splits off methyllithium yielding the corresponding silacycloalkane derivatives.In going from diethyl ether to THF as the solvent, the silyl shifts are more accelerated than the proton shifts.In no case, however, a Grovenstein-Zimmermann rearrangement involving phenyl migration took place.Degenerate silyl shifts starting from α-deuterated ω-(trimethylsilyl)alkyllithium compounds could not be detected either.Only by introduction of a second trimethylsilyl group into the 3 position a 1,3-(C -> C)-trimethylsilyl shift is initiated again.
Carbanion Rearrangements by Intramolecular 1,ω Proton Shifts, III. The Reaction of 2-, 3-, 4-, and 5-Phenylalkyllithium Compounds
Maercker, Adalbert,Passlack, Michael
, p. 540 - 577 (2007/10/02)
Upon addition of THF to a solution of 4-phenylbutyllithium (2) in diethyl ether a rapid intramolecular 1,4 proton shift takes place with the formation of 1-phenylbutyllithium (5).Similarly, although somewhat more slowly, 5-phenylpentyllithium (82) rearranges to 1-phenylpentyllithium (83) via 1,5 proton transfer.The corresponding rearrangements by 1,2 or 1,3 hydrogen shifts, however, starting with 2-phenylethyllithium (1) and 3-phenylpropyllithium (54), respectively, were not detected.With 3-phenylpropyllithium (54) a slow intramolecular 1,5 transfer an ortho proton is observed instead, yielding o-propylphenyllithium (100).The corresponding 1,6 shift with 4-phenylbutyllithium (2) was also detected in a minor amount in addition to the 1,4 proton shift already mentioned.There is no indication, however, for a 1,4 transfer of an ortho proton in 2-phenylethyllithium (1).The reaction products in this case can be exclusively explained by intermolecular transmetallation reactions.All ω-phenylalkyllithium compounds under investigation show interesting side and secondary reactions being rather different in deuterated solvents and in deuteriumfree solvents, respectively, due to the isotope effects.The analysis of the products is accomplished by 1H-NMR spectroscopy and, after derivatization, with the help of a GC-MS-combination.Stereoelectronic reasons are made responsible for the failure of the intramolecular 1,2 and 1,3 proton shift in these systems.
