Heptadienes—

Figure 2 76. A typical 2D Molflle of (2R,3f,5P)-2-hydro)cy-3,5-heptadiene nitrile with stereochemical flags (parity values, etc.) in the gray columns. For further explanation, see the text.

Figure 2-78. The stereochemistry of (2R,3 ,5 )-2-hydroxy-3,5-heptadiene nitrile can be expressed in the SMILES notation with or (back)slashes.

To a mixture of 0.10 mol of 1-ethoxy-l,2-heptadiene (see this chapter, Exp. 13) and 120 ml of diethyl ether was added 1 g of copper(I) bromide. A solution of butyl magnesium bromide in about 200 ml of diethyl ether, prepared from 0.25 mol of butyl bromide (see Chapter II, Exp. 5) was added in 15 min. The reaction was weakly exothermic and the temperature rose slowly to about 32°C. The mixture was held for an additional 40 min at that temperature, then the black reaction mixture was... 

The reaction of 1,2-heptadiene with iodobenzene in the absence of nucleophiles affords 2-phenyl-l,3-heptadiene (290) by /J-elimination of the 7r-allylpal-ladiuni intermediate) 182]. 

The principal coloring matter in turmeric and its oleoresin is curcumin [458-37-7] (l,6-heptadiene-3,5-dione, l,7-bis[4-hydroxy-3-methoxy-phenyl] (45), an orange-yeUow, crystalline powder, insoluble in water and ether but soluble in ethanol and glacial acetic acid. It has a reported melting point of 180-183°C. 

Diethenyloxiranes undergo thermal Cope-type rearrangements to oxacyclo-heptadienes (Scheme 16) (67AG(E)385) even when these are very strained intermediates (Scheme 17) (80JOC428). This process is particularly facile in fused-ring diethenyloxiranes like (16) (Chapter 5.17) and (17) (Chapter 5.07). 

This procedure illustrates a general method for the preparation of 2-hydroxybicyclo[3.2.0]heptanes by copper(I)-catalyzed photobicyclization of 3-hydroxy-1,6-heptadienes, and a general route to the requisite dienes from allyl alcohols by conversion to 4-pentenals and treatment of the latter with vinyl Grignard reagents. 

Cycloheptatrienes are in many cases in rapid equilibrium with an isomeric bicy-clo[4.1.0]heptadiene. The thermodynamics of the valence isomerism has been studied in a number of instances, and some of the data are given below. Calculate the equilibrium constant for each case at 25°C. Calculate the temperature at which K= for each system. Are the signs of the enthalpy and entropy as you would expect them to be Can you discern any pattern of substituent effects from the data ... 

Bicyclo[2.2.1]heptadiene rearranges at elevated temperatures to cycloheptatriene and toluene. The reaction is facilitated by substituents at C-7 such as phenyl and alkoxy, in which case cycloheptatrienes are the dominant products. 

Still another possibility of isomerization is illustrated by the easy interconversions between pentaphenylpentadienoie aeid chloride and 2-chloropentaphenyl-3-eyelopenten-l-one. Interestingly, 2,4,6-trimethylpjrrylium iodide maj be sublimed without decomposition in a vacuum, possibly as a covalent 6-iodo-4-methyl-3,5-heptadien-2-one or 2-iodo-2,4,6-trimethyl-2H-pyran valenee isomer. In a related case, chlorocyclopropenes are covalent and are converted into cyclo-propenium derivatives only by the action of Friedel-Crafts catalysts (electron-deficient metallic chlorides) (ef. also Section II,C, 2,c.)... 

Another application of catalyst 8 is to the reaction of acetylenic aldehydes [10c] (Scheme 1.18, Table 1.6). Two acetylenic dienophiles have been reacted with cyclo-pentadiene or cyclohexadiene to give bicyclo[2.2.1]heptadiene or bicyclo[2.2.2]octa-diene derivatives in high optical purity. A theoretical study suggests that this reaction proceeds via an exo transition state. 

This catalyst was successfully applied to the Diels-Alder reaction of propargyl aldehydes as dienophUes [12] (Scheme 1.21, Table 1.8). Though 2-hutyn-l-al and 2-oc-tyn-l-al are unreactive dienophUes, silyl- and stannyl-suhstituted a,/ -acetylenic aldehydes react with cydopentadiene readily in the presence of 20 mol% of the catalyst at low temperature to give hicyclo[2.2.1]heptadiene derivatives in high optical purity these derivatives are synthetically useful chiral building blocks. 

Due to the instability of the seven-membered heterocyclic ring, oxepin is prone to isomerization reactions to bicyclic heterocycles such as benzene oxide. Irradiation of oxepin with UV light of/. > 310 nm gives the isomeric 2-oxabicyclo[3.2.0]heptadiene(l) in high yield.12 207 At shorter wave lengths, phenol is formed predominantly.207... 

Under irradiation in diethyl ether, the dextrorotary enantiomer of 3,6-hexanooxepin-4-carb-oxylic acid rearranges to the oxabicyclo[3.2.0]heptadiene system with retention of the optical activity.36... 

The isomeric chloro-l-methylbenzo-2-azabicyclo[3.2.0]heptadienes 10a and 10b on heating under reflux in toluene rearrange in almost quantitative yields (90-95 %) to 9-chloro-l -methyl-1 H-benzazepine (11a) and its 6-chloro isomer lib, respectively.37... 

E)-3-methyl-2-pheriylsit fonyl-l,5-heptadien-4-ol yield 83% d.r. syn/anti) 90 10... 

Phoronediozonide (Sym-Diisopropylideneacetone-ozonide). C j 407, light green syrup, very expl, self-flammable on standing in air. Was prepd by Harries Turk by passing ozone thru a well cooled chloroformic soln of phorone [2,4-dimethyl-heptadien-(2,5)-on-(4)], (CH3)2C CH.CO,CH C(CH3)2, followed by vacuum removal of chlf at 20°... 

Phorone (Di iso p ropy lidene acetone, 2,6-dimethyl-2,5-heptadien-4-one). 

Selektiv gelingt die Reduktion einer C=C-Doppelbindung mit Lithiumalanat im 7-Hydroxy-bicyclo[2.2.1]heptadien zum anti-7-Hydroxy-bicyclo[2.2.1]hepten (—100% d.Th.)3 ... 

Hydroxy-3 -methyl-3-[4-methyl-pentcn-(3)-yl]-2-[2,6-dimethyl-heptadien-(l,5)-yl]- 660... 

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