L,5-Hexadien

The l,5-hexadien-3-ol derivatives 792 and 794 are cycli2ed to form the cyclo-pentadiene derivatives 793 and 795 by insertion of an alkene into -allylpalla-dium formed from allylic alcohols in the presence of trifluoroacetic acid (lO mol%) in AcOH[490],... 

Keto esters are obtained by the carbonylation of alkadienes via insertion of the aikene into an acylpalladium intermediate. The five-membered ring keto ester 22 is formed from l,5-hexadiene[24]. Carbonylation of 1,5-COD in alcohols affords the mono- and diesters 23 and 24[25], On the other hand, bicy-clo[3.3.1]-2-nonen-9-one (25) is formed in 40% yield in THF[26], 1,5-Diphenyl-3-oxopentane (26) and 1,5-diphenylpent-l-en-3-one (27) are obtained by the carbonylation of styrene. A cationic Pd-diphosphine complex is used as the catalyst[27]. 

AGE965, 86AGE1099, 880M2316). Species /x-h h -(2-benzyl-l,3,4,5-tetramethyl-2,3-dihydro-l,3-diborolyl)(i7 -allyl)(i7" -l,5-hexadiene)dinickel and /x-i7 i7 -[2-(2,4,6-trimethylbenzyl)-l,3,4,5-tetramethyl-2,3-dihydro-l,3-diborolyl](i7 -allyl)(i7" -l,5-hexadiene)dinickel serve as representative tripledecker complexes (01ZN(B)73). 

As we have indicated with our arrows, the mechanism of the uncatalyzed Cope rearrangement is a simple six-centered pericyclic process. Since the mechanism is so simple, it has been possible to study some rather subtle points, among them the question of whether the six-membered transition state is in the boat or the chair form. ° For the case of 3,4-dimethyl-l,5-hexadiene it was demonstrated conclusively that the transition state is in the chair form. This was shown by the stereospecific nature of the reaction The meso isomer gave the cis-trans product, while the ( ) compound gave the trans-trans diene. If the transition state is in the chair form (e.g., taking the meso isomer), one methyl must be axial and the other equatorial and the product must be the cis-trans alkene ... 

Similarly, Hammad and Wenthold have shown that l,4-dicyanocyclohexane-l,4-diyl radical anion forms spontaneonsly upon ionization of 2,5-dicyano-l,5-hexadiene (Eq. 5.13). 3... 

Cupery, M. E. et al., J. Amer. Chem. Soc., 1934, 56, 1167 During isolation of the title product from polymerised l,5-hexadiene-3-yne, high vacuum distillation must be carried only to a limited extent to prevent sudden explosive decomposition of the more highly polymerised residue. 

An investigation of different organic solvents, buffer, surfactants, and organorhodium compounds established that the catalytic reduction of tetralin using [ Rh(l,5-hexadiene)Cl 2] proceeds with high efficiency at high substrate-to-catalyst ratios. The reaction occurs at r. t. and 1 atm. pressure in a biphasic mixture of hexane and an aqueous buffer containing a low concentration of a surfactant which stabilizes the catalysts.314... 

In an electrochemical transformation of 111, 112 was obtained as product (equation 30)181 and 9,10-dicyanoanthracene (DCA) was used to photochemically initiate the reaction of 2,5-diphenyl-l,5-hexadiene (113) to 114 (equation 31)182. 

The asymmetric cyclization-hydrosilylation of 1,5-dienes has been also reported by use of a chiral yttrocene complex (Scheme 32).87 Highest enantioselectivity (50% ee) was observed for 3,3-dimethyl-l,5-hexadiene with diphenylsilane. 

Cyclopolymerization of Nonconjugated Dienes. Cyclopolymerization is an addition polymerization that leads to introduction of cyclic structures into the main chain of the polymer. Nonconjugated dienes are the most deeply studied monomers for cyclopolymerization and for cyclocopolymerizations with alkene monomers 66 In general, (substituted and unsubstituted) dienes with double bonds that are linked by less than two or more than four atoms cannot undergo efficient cyclization and result in crosslinked materials.12 In fact, efficient cyclopolymerization processes have been described, for instance, for a,oo-dienes like 1,5-hexadiene, 2-methyl-l,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene,67 73 which lead to formation of homopolymers and copolymers containing methylene-1,3-cycloalkane units. 

Knowles reported the hydrogenation of a-phenylacrylic acid and itaconic acid with 15% and 3% optical purity, respectively, by using [RhCl3(P )3] [P = (R)-(-)-methyl-n-propylphenylphosphine] as homogeneous catalyst [38]. Horner found that a-ethylstyrene and a-methoxystyrene can be hydrogenated to (S)-(+)-2-phe-nylbutane (7-8% optical purity) and (R)-(+)-l-methoxy-l-phenylethane (3-4% optical purity), respectively, by using the complex formed in situ from [Rh(l,5-hexadiene)Cl]2 and (S)-(-)-methyl- -propylphenylphosphine as catalyst [39]. 

Marko and coworkers [12] dehalogenated several alkyl and benzyl halides as well as halobenzenes (X=C1, Br, I) with [(l,5-hexadiene)RhCl]2/PPh3 in the presence of Et2NH using a medium of p-xylene/water at 50°C and atmospheric H2 pressure. Grushin and Alper [13] elaborated a similar (but more effective)... 

Hexachlorobenzene, conversion to pen-tachlorobenzoic acid, 44, 78 Hexachlorocyclopentadiene, ethylation to l,2,3,4,5-pentachloro-5-ethyl-cyclopentadiene, 43, 90 Hexadecanedioic acid, 43,39 l,5-Hexadien-3-ol, 41, 49... 

Phosphorus pentachloride, for conversion of pentaacetylgluconic add to add chloride, 41, 80 for oxidation of cycloheptatriene to tropylium fluoborate, 43, 101 with cyanoacetic acid, 41, 5 Phosphorus tribromide, reaction with l,5-hexadien-3-ol, 41, 50 Phthalic acids from thioimides, 44, 93 Phthalic anhydride, reaction with L-phenylalanine to yield N-phthaiyi-L-phenylalanine, 40, 82 Phthalic monoperacid, 42, 77 Phthaionic acid, 44, 63 N-Phthalyl-L-alanine, 40, 84 N-Phthalyl-0-alanine, 40, 84 N-Phthalylglydne, 40,84 N-Phthalyl-l-/3-phenylalanine, 40,82 PlMELIC ACID, (S-OXO-, DIETHYL ESTER, 42,41... 

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