Terminal double bond

If one is absolutely serious about ultra pure safrole then it can be separated from the eugenol-free sassafras oil by treatment with mercuric acetate [1,2,3,4] which likes that terminal double bond that only safrole has. The Hg(AcO)2 latches on to safrole at that double bond bringing it into solution as a solid sort of like the way that eugenol was. The safrole can then be separated from its still oily buddies by vacuum filtration. Safrole is then regenerated to its normal oily form by treatment with hydrochloric acid (HCI) which flicks the Hg(AcO)2 off the safrole and the safrole double bond reforms. As it so happens, the mercuric acetate also reforms intact so that it can be reused again such as in one of those... 

Conjugate addition of vinyllithium or a vinyl Grignard reagent to enones and subsequent oxidation afford the 1.4-diketone 16[25]. 4-Oxopentanals are synthesized from allylic alcohols by [3,3]sigmatropic rearrangement of their vinyl ethers and subsequent oxidation of the terminal double bond. Dihydrojasmone (18) was synthesized from allyl 2-octenyl ether (17) based on Claisen rearrangement and oxidation[25] (page 26). 

The oxidation of simple internal alkenes is very slow. The clean selectiv oxidation of a terminal double bond in 40, even in the presence of an internt double bond, is possible under normal conditions[89,90]. The oxidation c cyclic alkenes is difficult, but can be carried out under selected condition Addition of strong mineral acids such as HCIO4, H2S04 and HBF4 accelerate the oxidation of cyclohexene and cyclopentene[48,91], A catalyst system 0 PdSO4-H3PM06W6Oii(j [92] or PdCF-CuCF m EtOH is used for the oxidatioi of cyclopentene and cyclohexene[93]. 

The method was applied to the synthesis of (-t-)-l9-nortestosterone by the following sequence of reactions. Michael addition of the bisannulation reagent 124 to the optically active keto ester 129 and decarboxylation afforded 130, and subsequent aldol condensation gave 131. Selective Pd-catalyzed oxidation of the terminal double bond afforded the diketone 132 in 78% yield. Reduction of the double bond and aldol condensation gave ( + )-19-nortestosterone (133)[114]. 

The telomer 145 of nitroethane was used for the synthesis of recifeiolide (148)[121], The nitro group was converted into a hydroxy group via the ketone and the terminal double bond was converted into iodide to give 146. The ester 147 of phenythioacetic acid was prepared and its intramolecular alkylation afforded the 12-membered lactone, which was converted into recifeiolide (148),... 

The 3.8-nonadienoate 91, obtained by dimerization-carbonylation, has been converted into several natural products. The synthesis of brevicomin is described in Chapter 3, Section 2.3. Another royal jelly acid [2-decenedioic acid (149)] was prepared by cobalt carbonyl-catalyzed carbonylation of the terminal double bond, followed by isomerization of the double bond to the conjugated position to afford 149[122], Hexadecane-2,15-dione (150) can be prepared by Pd-catalyzed oxidation of the terminal double bond, hydrogenation of the internal double bond, and coupling by Kolbe electrolysis. Aldol condensation mediated by an organoaluminum reagent gave the unsaturated cyclic ketone 151 in 65% yield. Finally, the reduction of 151 afforded muscone (152)[123]. n-Octanol is produced commercially as described beforc[32]. 

The product of 1 4 addition 1 bromo 2 butene contains an internal double bond and so IS more stable than the product of 1 2 addition 3 bromo 1 butene which has a terminal double bond... 

Among chiral dialkylboranes, diisopinocampheylborane (8) is the most important and best-studied asymmetric hydroborating agent. It is obtained in both enantiomeric forms from naturally occurring a-pinene. Several procedures for its synthesis have been developed (151—153). The most convenient one, providing product of essentially 100% ee, involves the hydroboration of a-pinene with borane—dimethyl sulfide in tetrahydrofuran (154). Other chiral dialkylboranes derived from terpenes, eg, 2- and 3-carene (155), limonene (156), and longifolene (157,158), can also be prepared by controlled hydroboration. A more tedious approach to chiral dialkylboranes is based on the resolution of racemates. /n j -2,5-Dimethylborolane, which shows excellent enantioselectivity in the hydroboration of all principal classes of prochiral alkenes except 1,1-disubstituted terminal double bonds, has been... 

Includes cis, trans, and terminal double-bond isomers. 

The terminal double bond is active with respect to polymerisation, whereas the internal unsaturation remains in the resulting terpolymer as a pendent location for sulfur vulcanisation. The polymer is poly(ethylene- (9-prop5iene- (9-l,4-hexadiene) [25038-37-3]. 

Additive Polyimides. Rhc ne-Poulenc s Kin el molding compound and Kerimid impregnating resin (115), Mitsubishi s BT Resins (116), and Toshiba s Imidaloy Resin (117) are based on bismaleimide (4) technology. Maleic anhydride reacts with a diamine to produce a diimide oligomer (7). Eurther reaction with additional diamine (Michael addition) yields polyaminohismaleimide prepolymer with terminal maleic anhydride double bonds. Cure is achieved by free-radical polymerization through the terminal double bonds. 

If the bismaleimide-amine reaction is carried out with a deficiency of amine the polymer will have terminal double bonds which allows a cure site to give a thermosetting polymer via a double bond polymerisation mechanism. This approach was developed by Ciba-Geigy with their product P13N (Figure 18.42). 

When this stereoelectronic requirement is combined with a calculation of the steric and angle strain imposed on the transition state, as determined by MM-type calculations, preferences for the exo versus endo modes of cyclization are predicted to be as summarized in Table 12.3. The observed results show the expected qualitative trend. The observed preferences for ring formation are 5 > 6, 6 > 7, and 8 > 7, in agreement with the calculated preferences. The relationship only holds for terminal double bonds. An additional alkyl substituent at either end of the double bond reduces the relative reactivity as a result of a steric effect. 

The retron for the Claisen rearrangement transform (see above) is easily established by the application of a Wittig disconnection at each of the equivalent terminal double bonds of 57... 

The Wacker reaction can also be carried out for other olefins with terminal double bonds. With propene, for example, approximately 90% yield of acetone is obtained. 1-Butene gave approximately 80% yield of methyl ethyl ketone. 

Due to the presence of a terminal double bond in 1-butene, oxidation of this isomer via a chlorohydrination route is similar to that used for propylene. 

Recently a new constituent of pyrethrum extract was described by Godin et al. (9) jasmolin II, the cir-pent-2-enylrethronyl ester of pyrethric acid. Jasmolin II differs from pyrethrin II in that the terminal double bond of the alcoholic side chain is saturated. This constituent forms about 3% of the total pyrethrins. Jasmolin II is less toxic to the insects tested than a similar concentration of pyrethrins. The pyrethrum extract was 16 to 17 times as toxic as jasmolin II to Aedes aegypti and Fhaedon cochlearia adults, less than 17 times... 

Stein166 has indicated that the reactivity of the terminal double bond of the macromonomer (112) is 80% that of VAc monomer. The kinetics of incorporation of 112 have also been considered by Wolf and Burchard175 who concluded that 112 played an important role in determining the time of gelation in VAc homopolymerization in bulk. 

SELECTIVE EPOXIDATION OF TERMINAL DOUBLE BONDS 10,11-EPOXYFARNESYL ACETATE... 

Coupling of alkenylcarbene complexes and siloxy-substituted 1,3-dienes affords vinylcyclopentene derivatives through a formal [3C+2S] cycloaddition process. This unusual reaction is explained by an initial [4C+2S] cycloaddition of the electron-poor chromadiene system as the 471 component and the terminal double bond of the siloxydiene as the dienophile. The chromacyclohexene intermediate evolves by a reductive elimination of the metal fragment to generate the [3C+2S] cyclopentene derivatives [73] (Scheme 26). 

Chemoselectivity plays an important role in the benzannulation reaction as five-membered rings such as indene or furan derivatives are potential side products. The branching point is again the rf-vinylcarbene complex D intermediate which maybe formed either as a (Z)- or an ( )-metallatriene the (E)-configuration is required for the cyclisation with the terminal double bond. (Z)-Metallatriene D, however, leads to the formation of furan derivatives H (Scheme 8). Studies on the formation of (E)- and (Z)-isomers discussing stereoelectronic effects have been undertaken by Wulff [17]. 

The search for the racemic form of 15, prepared by allylic cyclopropanation of farnesyl diazoacetate 14, prompted the use of Rh2(OAc)4 for this process. But, instead of 15, addition occurred to the terminal double bond exclusively and in high yield (Eq. 6) [65]. This example initiated studies that have demonstrated the generality of the process [66-68] and its suitability for asymmetric cyclopropanation [69]. Since carbon-hydrogen insertion is in competition with addition, only the most reactive carboxamidate-ligated catalysts effect macrocyclic cyclopropanation [70] (Eq. 7), and CuPF6/bis-oxazoline 28 generally produces the highest level of enantiocontrol. 

Migrastatin (192) (Scheme 37) is a novel macrolide natural product that displays an inhibitory effect on the migration of human tumor cells. After an RCM-based synthesis of the 14-membered macrolide core of 192 [94], Danishefsky also achieved the first total synthesis of the natural compound [95], using the fully functionalized tetraene 191 as the metathesis precursor. Under the conditions shown in Scheme 37, the ring-closing step proceeded (E)-selectively with exclusive participation of the two terminal double bonds in 191, delivering only the ( , ,Z)-trienyl arrangement present in 192. 

Linear olefins (with terminal double bond or with internal double bond)... 

Liquid crystalline main chain polymers with siloxane spacer groups were obtained by the hydrosilation of (Si—H) terminated polydimethylsiloxane oligomers and mesogenic groups with terminal double bonds as shown in Reaction Scheme XVII-(a). Reactions were usually carried out in THF with the Wacker Oil catalyst 255). Completion of the reactions was followed by the disappearance of the strong (Si—H) absorption band at 2140 cm-1 using IR spectroscopy. 

With this rule in mind the outcome of CM-reactions can often be predicted. In the synthesis of organotrifluoroborate 79 [143] the terminal double bond is a type 1 substrate, while the 1,1-disubstituted olefin can be considered type III. The reaction of 2-methyl-1,4-pentadiene 77 with type II cross-partner 78 furnishes 79 efficiently (only 2 mol% catalyst used) in good yields after two steps. 

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