26981-77-1Relevant articles and documents
Reaction of μ-Oxobis with Group 14 Propargyl Derivatives and a Propargyl Ether
Gately, Daniel A.,Luther, Thomas A.,Norton, Jack R.,Miller, Mary M.,Anderson, Oren P.
, p. 6496 - 6502 (2007/10/02)
The treatment of 4,4-dimethyl-1-(trimethylsilyl)-2-pentyne (4a) or 4,4-dimethyl-1-(tributylstannyl)-2-pentyne (4b) with μ-oxobis (2) gives 4,4-dimethyl-1-(2-iodophenyl)-2-pentyne (9).Deuterium labeling has confirmed that propargylation of 2 occurs ortho to the position originally occupied by the I(III).The addition of 2 equiv of 4a to 2 at -80 deg C results in 2 equiv of 9, trimethylsilyl triflate (10), and tert-butylallene (11) and 1 equiv of hexamethyldisiloxane (12); in contrast, the addition of 2 equiv of 4b to 2 at -30 deg C results in 2 equiv each of 9 and tributylstannyl triflate (16).A mechanism that explains these product ratios is proposed.The reaction of 2-o,o'-d2 and 4b shows the negligible intramolecular kinetic isotope effect (0.99 +/- 0.01) expected for what is in effect a Claisen rearrangement.The addition of 2 to 2-butynyl (trimethylsilyl)methyl ether (20) affords the single product 21 resulting from anti addition and control of regiochemistry by the ether oxygen.Attempts to desilylate 21 to an allenyl triflate result in the regeneration of the propargyl ether 20.
Allylic and Propargylic Substitution Reactions Involving Radicals Generated from Alkylmercury Halides
Russell, Glen A.,Ngoviwatchai, Preecha,Wu, Yuh Wern
, p. 4921 - 4927 (2007/10/02)
Addition of alkyl radicals to allyl or propargyl derivatives forms adduct radicals which can undergo β-elimination with substituents such as halogen, PhS, PhSO2, Bu3Sn, or HgCl to form the alkyl-substituted propene or allene and an eliminated radical which regenerates the alkyl radical by displacement from an alkylmercurial.With β-oxy substituents, such as O2CR, OP(O)(OEt)2, O3SAr, OPh, OSiMe3, or OH, the adduct radicals can displace the alkyl radical from the alkylmercurial to yield β-substituted alkylmercurials which spontaneously, or in the presence of nucleophiles, undergo an elimination reaction to yield the alkene or allene.Relative reactivities toward tert-butyl radical attack, such as k(allyl chloride)/k(propargyl chloride) = ca. 10, have been determined.A similar relative reactivity is observed in reaction with (t-Bu)2CuLi implicating attack by free tert-butyl radicals.With allyl or propargyl iodide, radical attack leads to iodine atom abstraction.Reaction of propargyl iodide with t-BuHgCl/hν, (t-Bu)2CuLi, or (t-Bu)3ZnLi leads to a mixture of hydrocarbons in which tert-butylallene is present in only trace amounts.Benzene is an important reaction product which seems to be formed via the cyclodimerization of two "propargyl" (C3H3.) radicals.
