2.5- diphenyl-1,5-hexadiene

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]. 

Substituents which do not change the overall reaction energy may still have an influence on the TS geometry. Consider for example 2,5-diphenyl-1,5-hexadiene. The... 

The rearrangement proceeds from the Si-state of the 1,4-diene 1. The Ti-state would allow for different reactions like double bond isomerization. Rigid systems like cyclic dienes, where EfZ -isomerization of a double bond is hindered for steric reasons, can react through the Ti-state. When the rearrangement proceeds from the Si-state, it proves to be stereospecific at C-1 and C-5 no -isomerization is observed. Z-l,l-Diphenyl-3,3-dimethyl-l,4-hexadiene 5 rearranges to the Z-configured vinylcyclopropane 6. In this case the reaction also is regiospecific. Only the vinylcyclopropane 6 is formed, but not the alternative product 7. ... 

Der Bis-[2-phenyl-2-cyan-vinyl]-ather (1) wird iiberwiegend zum 2,5-Diphenyl-hexen-(2)-disdure-nitril (III) reduziert. Je nach Kathodenpotential wird zusatzlich 2,5-Diphe-nyl-hexadien-(2,4)-disaure-dinitril (II) bzw. bei 2 V das 2,5-Diphenyl-hexandisaure-dinitril (IV) erhalten. Da es sich hier primar um die Rekombination zweier radikalischer Spaltprodukte des Athers I handelt, ist cine hohe Depolarisator-Konzentration vorteil-haft2 ... 

Some mechanisms of radical-initiated migration copolymerization of di-alkyl(diphenyl)stannanes with non-conjugated epoxyalkadienes such as 4,4-epoxy-l,7-heptadiene (I) and 3-glycidyl-oxy-l,6-hexadiene (II) have been discussed 98). 

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. 

A diradical intermediate appears to be formed in the rearrangement of 2, 5 diphenyl-1, 5-hexadiene probably due to the phenyl groups stabilizing the radical centres. 

Diphenylcarbodiaxone [called C-Hydroxyr diphenyltetrazolium Betaine or 1,2-Diphenyl-5-oxa-l,2,3,6-tetrazabicyclo [2.1.1]-1(6),3-hexadiene in CA Coll Formula Index 14-40 (1920-46), p718 [(called Diphenylcarbodiazon or Anhydrid of 2.3-Diphenyl-5-oxytetrazolium-hydroxid in Ger)... 

Photolysis of l,6-diazido-2,5-diphenyl-3,4-diaza-2,4-hexadiene (679) afforded 3,6-diphenyl-l,2,4-triazine (680) in 21% yield (72CL1185). 

The fluorescence of DCA is also quenched efficiently by 2,5-diphenyl-l,5-hexadiene with a nearly diffusion-limited rate constant in MeCN (1.1 x 10lodm3 mol-1 s ), since the photoinduced electron transfer from the diene ( ° = 1.70 V vs. SCE) to DCA (E ed = 1.91 V vs. SCE) [170] is exergonic [184], The photoinduced electron transfer induces Cope rearrangement of the diene via the cyclohexane-1,4-radical cation intermediate. In... 

When C3 of the 1,4-pentadiene is disubstituted as in 69, the rearrangement is stereospecific at carbons 1 and 5. For example, m-1,1 -diphenyl-3,3-dimethyl-1,4-hexadiene (73) rearranges to 74, in which the side chain is cis, but trans-, -diphenyl-3,3-dimethyl-1,4-hexadiene (75) rearranges to 76, in which the side... 

A sub case in this category is the benzylation of enolates through the Srn 1 process. In this way, both a-nitro- and a-chloro-4-nitrocumene are alkylated by the enolates of 2-nitropropane, diethylmalonate, or diethyl 2-butylmalonate. A particular case of benzylic C-C fragmentation is the electron transfer photosensitized Cope rearrangement of 2,5-diphenyl-1,5-hexadienes [218,219]. 

The 1,4-disubstituted cases are degenerate, so no averaging is needed. The chameleonic model suggests that the substituent effects should be additive, or a predicted value of A/ = 31.6 kcal mol for l,4-dicyauo-l,5-hexadiene and AH = 31.4 kcal mol for l,4-diphenyl-l,5-hexadiene. The computed barriers are actually lower thau these values. The barrier for the 1,3,4,6-tetrasubstituted... 

The alkyne complex (68) reacts with two equivalents of ethene to give the 5-cfr-3,4-( )-diphenyl-l,3-hexadiene complex (69) as shown in Scheme 39. Use of 2-butyne leads to the metallacycle (70) via bis(alkyne) complex. " The bicyclic vanadacyclopentatriene complex (71) is formed from 1,7-nonadiyne. 

HYDROXYDIPHENYL see BGJ250 p-HYDROXYDIPHENYL see BGJ500 4,4 -HYDR0XY-Y,A-DIPHENYL-PA-HEXADIENE see DAL600... 

Carbocyclic compounds can be formed by the nucleophilic intramolecular capture of a seleniranium intermediate of an olefinic bond. The carbonium ion which is formed as intermediate can react with another nucleophile or with the solvent. The first examples of these carbocyclization reactions were observed with dienes. Clive [105] reported that the reaction of the diene 203 with phenyl-selenyl chloride in acetic acid afforded the intermediate 204 which reacted with the solvent to give the bicyclic compound 205 (Scheme 31). Carbocyclization reactions were efficiently promoted by phenylselenyl iodide produced by diphenyl diselenide and iodine. As indicated in Scheme 31,Toshimitsu reported that the reaction of 1,5-hexadiene 206, in acetonitrile and water, afforded the acetamido cyclohexane derivative 209, derived from the cyclization of the seleniranium intermediate 207 followed by the reaction of the carbocation 208 with acetonitrile [106]. In several cases, carbocyclization reactions can be more conveniently effected by independently generating the seleniranium intermediates. A simple procedure consists of the reaction of trifluoromethane-sulfonic acid with j9-hydroxyselenides, which can be easily obtained from the... 

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