Oxidation 1, 7-octadiene

HOaQCHjlfiCOiH, CSH14O4. Important dicarboxylic acid obtained by oxidizing ricino-leic acid (from castor oil) also obtained by oxidation of cyclo-octene or cyclo-octadiene formerly obtained from cork. Used in the formation of alkyd resins and polyamides. Esters are used as plasticizers and heavy duty lubricants and oils. 

Acetoxy-l,7-octadiene (40) is converted into l,7-octadien-3-one (124) by hydrolysis and oxidation. The most useful application of this enone 124 is bisannulation to form two fused six-membered ketonesfl 13], The Michael addition of 2-methyl-1,3-cyclopentanedione (125) to 124 and asymmetric aldol condensation using (5)-phenylalanine afford the optically active diketone 126. The terminal alkene is oxidi2ed with PdCl2-CuCl2-02 to give the methyl ketone 127 in 77% yield. Finally, reduction of the double bond and aldol condensation produce the important intermediate 128 of steroid synthesis in optically pure form[114]. 

Base-induced rearrangement of bicyclo[2.2.2]octane oxide 67 gives predominantly bicyclo[2.2.2]octanone 68 (Scheme 5.15), which once again indicates that close proximity between the carbenoid center and the C-H bond into which it may insert is important if such an insertion is to occur [30]. In comparison, the sense of product distribution is reversed for the related substrate bicyclo[2.2.2]octadiene oxide 70 on treatment with LDA [15, 22], alcohol 72 being the favored product. 

The product is 2,7-octadien-l-oI which can be dehydrogenated/hydrogenated internally to give 7-octenal, which can be hydroformylated to the dialdehyde, nonadialdehyde, and then hydrogenated to nonadiol. The initial product can be hydrogenated to 1-octanol the dialdehyde can be oxidized to the diacid. The catalyst used is Pd modified with the Li salt of monosulphonated triphenylphosphine. 

The most characteristic reaction of butadiene catalyzed by palladium catalysts is the dimerization with incorporation of various nucleophiles [Eq. (11)]. The main product of this telomerization reaction is the 8-substituted 1,6-octadiene, 17. Also, 3-substituted 1,7-octadiene, 18, is formed as a minor product. So far, the following nucleophiles are known to react with butadiene to form corresponding telomers water, carboxylic acids, primary and secondary alcohols, phenols, ammonia, primary and secondary amines, enamines, active methylene compounds activated by two electron-attracting groups, and nitroalkanes. Some of these nucleophiles are known to react oxidatively with simple olefins in the presence of Pd2+ salts. Carbon monoxide and hydrosilanes also take part in the telomerization. The telomerization reactions are surveyed based on the classification by the nucleophiles. 

Thus, the oxidation potential of the former type of diene (limonene) is substantially the same as that of the corresponding monoolefin (1-Me-cyclohexene), whereas norbor-nadiene and bicyclo[2.2.2]octadiene show much lower oxidation potentials than those of norbornene and cyclohexene. 

The metal-catalysed autoxidation of alkenes to produce ketones (Wacker reaction) is promoted by the presence of quaternary ammonium salts [14]. For example, using copper(II) chloride and palladium(II) chloride in benzene in the presence of cetyltrimethylammonium bromide, 1-decene is converted into 2-decanone (73%), 1,7-octadiene into 2,7-octadione (77%) and vinylcyclohexane into cyclo-hexylethanone (22%). Benzyltriethylammonium chloride and tetra-n-butylammo-nium hydrogen sulphate are ineffective catalysts. It has been suggested that the process is not micellar, although the catalysts have the characteristics of those which produce micelles. The Wacker reaction is also catalysed by rhodium and ruthenium salts in the presence of a quaternary ammonium salt. Generally, however, the yields are lower than those obtained using the palladium catalyst and, frequently, several oxidation products are obtained from each reaction [15]. 

Oxidation of 1,5-dienes to c -tetiahydrofurandiols was accomplished with RuO /aq. Na(10 )/acetone-EtOAc thus 2,5-dimethyl-1,5-hexadiene gave tetrahydrofurandiol, geranyl acetate yielded cw-tetrahydrofurandiol, and trans, tra 5-2,6-dimethyl-2,6-octadiene-l,8-diol diacetate (1) gave tetrahydrofuran ketol diacetate (2) (Fig. 3.12 cf. mech. Ch. 1) [174],... 

Oxidative cyclisation of 1,6-dienes to trani-2,6-bis(hydroxyl-methyl)-tetrahy-dropyranyl-diols was effected by RuClj/aq. Na(lO )/CH3CN-EtOAc/0°C 1,6-heptadiene (1) and 7-methyl-l,6-octadiene (2) were so oxidised (Fig. 3.13 cf. mech. Ch. 1) [184],. 

Fig. 3.12 Oxidation by RuO of 2,6-dimethyl-2,6-octadiene-l,8-diol diacetate (1) to tetrahydrofuran ketol diacetate (2) [174]...

Mori has reported the nickel-catalyzed cyclization/hydrosilylation of dienals to form protected alkenylcycloalk-anols." For example, reaction of 4-benzyloxymethyl-5,7-octadienal 48a and triethylsilane catalyzed by a 1 2 mixture of Ni(GOD)2 and PPhs in toluene at room temperature gave the silyloxycyclopentane 49a in 70% yield with exclusive formation of the m,//7 //i -diastereomer (Scheme 14). In a similar manner, the 6,8-nonadienal 48b underwent nickel-catalyzed reaction to form silyloxycyclohexane 49b in 71% yield with exclusive formation of the // /i ,// /i -diastereomer, and the 7,9-decadienal 48c underwent reaction to form silyloxycycloheptane 49c in 66% yield with undetermined stereochemistry (Scheme 14). On the basis of related stoichiometric experiments, Mori proposed a mechanism for the nickel-catalyzed cyclization/hydrosilylation of dienals involving initial insertion of the diene moiety into the Ni-H bond of a silylnickel hydride complex to form the (7r-allyl)nickel silyl complex li (Scheme 15). Intramolecular carbometallation followed by O-Si reductive elimination and H-Si oxidative addition would release the silyloxycycloalkane with regeneration of the active silylnickel hydride catalyst. 

Preparation of (—)-Citronellol from Optically Active Pinenes. (+)-ci5-Pinane is readily synthesized by hydrogenation of (+)-0 -pinene or (+)-/3-pinene, and is then pyrolyzed to give (+)-3,7-dimethyl-l,6-octadiene. This compound is converted into (-)-citronellol (97% purity) by reaction with triisobutylalumi-num or diisobutylaluminum hydride, followed by air oxidation and hydrolysis of the resulting aluminum alcoholate [50]. 

Diethyl-3,5-octadiene 174 Dithiane oxides alkylation of 84 carbanions of 84 Dithianes alkylation of 76,79 as acyl anion equivalents 75 carbanions of 76,79 cleavage of 14-18.76,79 desulfurization of 78 oxidation of 23... 

In the same year the biotransformation of these monoterpenes by B. cinerea in model solutions was described by another group [41]. Although the major metabolites found were co-hydroxylation compounds, it is important to note that these authors only identified the -isomers in the extracts and that some new compounds were detected that were not described by the previous group, Fig. (9). Geraniol (20) was mainly transformed to (2 ,5 )-3,7-dimethyl-2,5-octadiene-l,7-diol (53), ( )-3,7-dimethyl-2,7-octadiene-l,6-diol (54) and (2 ,6 )-2,6-dimethyl-2,6-octadiene-1,8-diol (43), nerol (14) to (2Z,5 )-3,7-dimethyl-2,5-octadiene-1,7-diol (55), (Z)-3,7-dimethyl-2,7-octadiene-l,6-diol (56), and (2E,6Z) 2,6-dimethyl-2,6-octadiene-1,8-diol (47). Furthermore a cyclisation product (57) was formed which was not previously described. Finally citronellol (4) was converted to trans- (60) and cw-rose oxide (61) (a cyclisation product not identified by the other group), ( )-3,7-dimethyl-5-octene-l,7-diol (58), 3,7-dimethyl-7-octene-l,6-diol (59) and ( )-2,6-dimethyl-2-octene-1,8-diol (34). 

The biotransformation of linalool by Botrytis cinerea has also been described [60]. After addition of linalool to botrytised must, a series of transformation products was identified (E)- (49) and (Z)-2,6-dimethyl-2,7-octadiene-l,6-diol (48), trans- (76) and cw-furanoid linalool oxide (77), trans- (78) and c/s-pyranoid linalool oxide (79) and their acetates (80, 81), 3,9-epoxy-p-menth-1 -ene (75) and 2-methyl-2-vinyltetrahydrofuran-5-one (66) (unsaturated lactone), Fig. (11). Quantitative analysis however, showed that linalool was predominantly (> 90%) metabolised to ( )-2,6-dimethyl-2,7-octadiene-l,6-diol (49) by B. cinerea. The other compounds were only found as by-products in minor concentrations. 

Nitrodienes undergo intermolecular Diels-Alder reactions with appropriate dienophiles. The resulting nitro compounds can then be cyclized via a nitrile oxide intermediate.49 Thus, the 2-chloroacrylonitrile Diels-Alder adduct of 8-nitro-l,3-octadiene was prepared and cyclized to give (105) as a 3 1 mixture of diastereomers (Scheme 30). The Diels-Alder adduct of dimethyl acetylenedicarboxylate and 8-nitro-l,3-octadiene cyclized exclusively at the conjugated double bond, activated by the ester groups. Similarly, the quinone Diels-Alder adduct (106) cyclized at the conjugated double bond reduction of the conjugated double bond permitted cyclization on the cycloalkenyl double bond. 

The reaction is very slow in acetic acid alone, and accelerated as acetate by the addition of bases [59]. These two isomers undergo Pd-catalysed allylic rearrangement with each other. 3-Acetoxy-l,7-octadiene (139) is converted to the allylic alcohol 157 and to the enone 158, which is used as a bisannulation reagent [60], Thus Michael addition of 158 to 2-methylcyclopentanedione (159) and aldol condensation give 160. The terminal alkene is oxidized using PdCl2/CuCl/02 to the methyl ketone 161. After reduction of the double bond in 161, aldol condensation affords the tricyclic system 162. 

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