1,3,7-Octatriene, preparation

Benzannulated azocines can be prepared starting from 4-phenyl-l,2.3-benzotriazine (16), flash-vacuum pyrolysis of which leads to 2-phenylbenzazete (17) (cf. Houben-Weyl. Vol. E16c, p 939), which is stable until about 40 °C and easily enters into cycloaddition reactions with dienes. With tetraphenylcyclopentadienone, a nonisolable adduct is formed which, by loss of carbon monoxide, gives an azabicyclo[4.2.0]octatriene derivative that isomerizes to the 1 -benzazocine 18.22... 

Another way to prepare 1,3,7-octatriene is to eliminate phenol from 8-phenoxy-1,6-octadiene (23) by heating in the presence of palladium and PPh3 (28 ) ... 

As for compounds having modified bridges in a bicyclo[2.2.2]octatriene system, 1 -rm-butyl-1,4-dihydronaphthalene 1,4-endoxides (109) and 9-rm-butyl-l,2,3,4-tetrachloro-9,10-dihydro-9,10-ethenoanthracene (110) were prepared. The... 

In water-heptane biphasic systems, allylic alcohols underwent rearrangement to the corresponding carbonyl compounds with a catalyst prepared in situ from RhCU.aq and TPPTS. The reactions proceeded very fast (TOP up to 2500 h ) and in most cases provided the carbonyl products quantitatively. The industrially interesting geraniol was isomerized mostly to citronelM, albeit octatrienes and tricyclene were also produced. With an increase of the pH of the aqueous phase the yield of isomerization decreased somewhat (from 48 % to 40 %), however the selectivity towards the... 

Two patents by Takahashi et al. reported the synthesis of vitamin A via a Cio dihalogeno derivative [34,35]. In one procedure the halogenodiene was prepared by bromination of 3,7-dimethyl-2,5,7-octatrien-1-yl acetate. Addition of the latter and /BuOK in DMF to the Cio sulfone provided the retinol sulfone (34%). Again, double elimination (MeOK), gave vitamin A acetate, Fig. (13). 

Like its hydrocarbon analogue, it exists in thermal equilibrium with its octa-fluorobicyclo[4.2.0]octatriene valence isomer 52, as shown in Eq. (3) Keq = 0.003 at 20°C in acetone-d6) (123). Valence isomer 52 can be prepared independently, but has a half-life of only 14 min at 0°C (124). OFCOT undergoes a photochemical ring closure to give a 20 1 mixture of the anti- and syn-tricyclic valence isomers 53 and 54, which in turn can be converted thermally back to OFCOT at 150°C (125). 

Dimerization of isoprene, if carried out regioselectively to give the head-to-tail dimer 97, would be useful for terpene synthesis. So far few reports on successful regioselective dimerization of isoprene have been given, and this remains an unsolved problem. 2,6-Dimethyl-1,3,6-octatriene (97), the head-to-tail dimer, can be prepared with high selectivity using Zr [36], Ni [37,38] and Pd [39] catalysts. However, selective functionalization of this dimer to the terpene alcohol 98 is not easy. 

The preparation of substituted diphosphabicyclo-octatrienes or diphosphabarre-lenes (lO) was achieved by Krespan, McKusick and Cairns by direct reaction of red phosphorus with fluorinated acetylenes in the presence of a catalytic amount of iodine at 200 for 8 h under pressure. The reaction might possibly go through a diphosphorin intermediate (9), since phosphorin readily... 

A total of 0.11 g (0.4 mmol) of Ni(cod), is dissolved in 5 ml, of toluene in a lube with a Teflon tap. Then 0.4 mmol of aminophosphinite ligand (D)-FphosNH is dissolved in 5 mL of toluene and 2.0 g of internal standard (heptane or decane) are added. This solution is introduced under N, into the reaction tube and the diene (piperylene) is then added under N2. The tube is then closed and put into a LhermoslalLed bath (40 C) where the solution is stirred with a magnetic stirrer. At the end of the reaction (3 h), the mixture is filtered over silica gel to eliminate the nickel catalyst, and the mixture is analyzed by GC and separated via preparative chromatography and distillation. With 95% conversion of the diene the product contains 16% ( ,Z)-4,5-dimethyI-l,3,6-octatriene (90% ee, NMR) and 12% ( , )-4,5-dimcthyl-l,3,6-octatriene (35 % ee, NMR) besides other (achiral) products. At lower conversions (75% after 0.75 h) the contents of the two chiral isomers are 21 % and 70%, respectively. 

An analogous cyclooctatetraene complex can be prepared by displacement of hexadiene from a bis(i -allyl) complex with butadiene. The resulting allylic, CgHj -containing complex is a catalyst for the dimerization of butadiene to 1,3,6-trans,cis-octatriene ... 

Kuhn et al.910 prepared octatrienal by condensation of two molecules of crotonaldehyde ... 

Borahydrindane (1) and lO-methyl-9-boradecalin (10) were prepared in situ by hydroboration of 1,3,7-octatriene (13) and 5-methyl-1,4,8-nonatriene (14), respectively (Equations (1) and (2)) <85JOC520>. 

The 1,3-butadiene cyclo-dimerization reaction can be performed by iron complexes, prepared in situ by the reduction of [Fe2(NO)4Gl2l with metallic zinc, dissolved in [G4GiIm][BF4] or [G4GiIm][PF6] ILs (Scheme 30). The linear dimerization of 1,3-butadiene can also be performed with Pd(ii) salts (chloride or acetate)/PPh3 catalyst precursor dissolved in [G4GiIm]BF4 or [G4GiIm]PF6 to produce 1,3,6-octatriene (Scheme 31). ... 

Aspects of cyclo-octatetraene chemistry have been reviewed. The crystal structure of perchlorocyclo-octatetraene has been examined. Potassium amide in liquid ammonia has been used to remove two protons from cis- and trans-bicyclo[6,2,0]-deca-2,4,6-triene to give the dianion (276) which is stable in solution and can be oxidized by iodine to the cyclo-octatetraene (277). Similarly the unstable tricyclic cyclo-octatetraene-cyclo-octatriene (278) was prepared from the corresponding biscyclo-octatriene. Treatment of (278) with potassium amide in liquid ammonia gives a deep-purple solution which may contain the dianion (279). ... 

Octamethylbicyclo[4,2,0]octatriene (285) has been prepared by elimination of nitrogen at low temperature from (286). The bicyclic triene reverts to its monocyclic isomer, = 322 min at 5 °C, and the equilibrium mixture at 35 °C contains over 95 % of the monocyclic isomer (286). The diene reacts readily at 0° with dienophiles such as maleic anhydride to give the expected adducts (287). 

A stable crystalline bicyclo[4,2,0]octatriene has been prepared.Photodecar-bonylation of the dione (288) gave 2,3,4,5-tetrachlorobicyclo[4,2,0]octatriene (289) as crystals m.p. 38 °C. Isomerization to the tetrachlorocyclo-octatetraene (290) occurred at 60 °C, = 15 min, and the conversion was essentially quantitative. Bond... 

Kitahara and co-workers have prepared derivatives of 5,8-dimethylene-1,5-cyclo-octatriene by thermal ring opening of the related 2,5-dimethylenebicyclo[4,2,0]-octa-3,7-dienes. 

The radical anion of 7,8-dimethylene-1,3,5-cyclo-octatriene has been prepared, but the transformation to the cyclobutene does not take place under the conditions used. ... 

Hydrogenation of olefinic ligands in zerovalent complexes is a fadle method for the synthesis of metal organosols. Hydrogenation of (cydooctadiene)(cydo-octatriene)ruthenium, Ru(COD)(COT), yidds metaUic ruthenium, and, in the presence of polymers such as PVP, ceUulose nitrate, and cellulose acetate, ruthenium sols form. [23, 113] For the PVP stalnlized sol, the partide rize is very small (ca. 1 nm). Similar reactions of Ni(COD)2, Pt(COD)Q2, or mixtures of the two have been used to prepare PVP stabilized mono- and tnmetallic organosols of these metals. [114]... 

The Pd-catalyzed elimination is extended to the synthesis of conjugated trienes and tetraenes. Reaction of ( , )-hexadienyl acetate gave (Ej-hexatriene exclusively (>EIZ = 97 3) in 87% yield. On the contrary an 80 20 mixture of isomeric E- and Z-hexatrienes was formed in 67% yield in the reaction of 3-acetoxy-l,5-hexadiene. ( , )-l,3,5,7-Octatriene was also prepared from ( , , )-2,4,6-octatrienyl acetate (Scheme 7). 

Cyclo-octa-5,7-diene-l,4-dione was obtained in excellent yield by flash thermolysis of bicyclo[4,2,0]oct-7-ene-2,5-dione at 500 °C and was converted by bromination-dehydrobromination into cyclo-octa-2,5,7-triene-l,4-dione. The amino-benzocyclo-octatriene (79) was prepared by treatment of the 1,2-dihydro-isoquinoline (80) with add under reflux followed by a Hofmann degradation. ... 

T)-tritylcyclo-octatetraene) iron has been prepared in two steps from tricarbonyl octatetraene)iron. Treatment with cerium(iv) salts released free tritylcyclo-octatriene and protonation gave the tricarbonyl(l-5-ri-6-tritylcyclo-octa-2,4,6-trienylium)iron cation (220). Thermolysis at 160 °C gave tricarbonyl[2,3 4,5-Ti-7-tritylbicyclo[4,2,0]-octa-2,4,7-triene]iron. ... 

A great number of catalysts active in dimerization of isoprene is known. Ziegler-type catalysts prepared by an aluminum compound and a titanium-, cobalt-, zirkonium-, iron- or vanadium compound yield, besides cyclic products [85—87], mostly the linear tail-to-head dimer 2,6-dimethyl-l,3,6-octatriene [88—95]. Only in a few cases, is the tail-to-tail product 2,7-dimethyl-1,3,6-octatriene also formed [86]. Using nickel catalysts, the tail-to-tail dimer 2,7-dimethyl-1,3,7-octatriene is generally the main product [96—98], but also the head-to-tail dimer allocymene can be obtained [99]. 

Pyrolysis of (130) gives (131), possibly ina the cis,trans,cis-cyclohepta-l,3,5-triene (132) the Diels-Alder adduct (133), ostensibly of the parent cis, trans,cis-cyclo-octatriene, was prepared indirectly from the adduct of furan and trans,cis-cyclo-octa-2,4-dien-l-one, and the retro-Diels-Alder reaction was studied at 180°C. ... 

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