22430-49-5Relevant articles and documents
Preparation of tert-Butyl-Capped Polyenes Containing up to 15 Double Bonds
Knoll, Konrad,Schrock, Richard R.
, p. 7989 - 8004 (1989)
7,8-Bis(trifluoromethyl)tricyclo2,5>deca-3,7,9-triene (TCDT) can be ring-opened in a controlled manner by W(CH-t-Bu)(NAr)(O-t-Bu)2 (Ar = 2,6-C6H3-i-Pr2) to give living oligomers from which the metal can be removed in a Wittig-like reaction with pivaldehyde or 4,4-dimethyl-trans-2-pentenal.Heating the oligomer yields a distribution of tetr-butyl-capped polyenes, (t-Bu)(CH=CH)n(t-Bu), where n is odd if pivaldehyde is used in the cleavage reaction or even if 4,4-dimethyl-trans-2-pentenal is used.Mixtures of odd and even polyenes have been analyzed byreserved-phase HPLC methods, and those having as many as 13 double bonds have been isolated by column chromatography on silica gel under dinitrogen at -40 deg C and characterized by (1)H and (13)C NMR and UV-vis studies.The 17-ene has been observed by HPLC.Polyenes containing more than 17 double bonds are relatively unstable under the reaction and subsequent isolation conditions; those containing between 11 and 15 double bonds decompose thermally progressively more readily.The initial isomer in the odd-ene series has largely the trans(cis,trans)x geometry as a result of stereospecific trans initiation, stereoselective trans propagation, stereospecific trans cleavage, and stereospecific cis retro-Diels-Alder reactions.The even-ene series is more complex since the Wittig-like reaction involving 4,4-dimethyl-trans-2-pentenal is not selective.UV-vis and (13)C and (1)H NMR data have been collected and analyzed in detail for the trans(cis,trans)x isomers for x = 1-5 (up to 11 double bonds) and for the odd and even all-trans forms containing up to nine double bonds.Extrapolation of a plot of the energy of the 1Bu 1Agg(0-0) transition versus 1/n (for up to the 13-ene) predicts that the HOMO-LUMO gap will be 1.79-1.80 eV for an infinite all-trans-polyene; in carbon disulfide it will be 1.56 eV.For the trans(cis,trans)x forms the 1Bu 1Agg(0-0) energy gap is predicted to be 1.95 eV for an infinite polyene in a mixture of acetonitrile, dichloromethane, and water (90:5:5).The ease of thermal cis-to-trans isomerization (ultimately to the all-trans form) correlates directly with chain length, isomerization to the all-trans form being especially facile for the 13-ene and beyond.The all-trans-polyenes are significantly less soluble than forms that contain one or more cis double bonds, although cross-linking cannot be ruled out as a contributor to insolubility for polyenes longer than the 13-ene.The retro-Diels-Alder reaction in the first unit away from the metal in living polyTCDT is accelerated 10 times relative to that in the second unit away from the metal.Heating polyTCDT gives living polyenes that are stable at 50 deg C for 45 min in solution; no benzene is formed.
Mercury in Organic Chemistry. 36. Synthesis of (?-Allyl)palladium Compounds and 1,4-Dienes via Vinylpalladation of Monocyclic Alkenes
Larock, Richard C.,Takagi, Kentaro
, p. 4329 - 4332 (2007/10/02)
The reaction of vinylmercuric chlorides, cyclic alkenes, and Li2PdCl4 in tetrahydrofuran affords (?-allyl)palladium compounds 1.When the reaction is run in the presence of triethylamine, the corresponding 1,4-dienes 2 are obtained instead.These reactions
