L,6-heptadiene

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

Selective hydraformylation of nonconjugated dienes can be carried out such that the least-hindered double bond reacts. Thus citronellene (entry 6) and 2,6-dimethyl-l,5-heptadiene both undergo preferential reaction at the least-substituted double bond, the hydroformylation of citronellene patterned after that of 3-methyl-1-pentene (Table 1) and the hydroformylation of 2,6-dimethyl-l,5-heptadiene to citronellal following that of 2-methyl-1-pentene, avoiding placing the formyl group at the quaternary carbon. The reaction of limonene (entry 8) shows similar behavior. 

Etherification.1 In the presence of BuSnClj, 1,4- and 1,5-diols are converted into acyclic and cyclic ethers. The actual catalyst is an organoalkoxytin dihalide, BuSn(OR)Cl2. This dehydration of l,5-heptadiene-4-ol (1) results in three acyclic ethers with 2 being the major product. 

In 1980, we reported the structure of the Comstock mealybug, Pseudococcus comstocki (Kuwana), pheromone as 2,6-dimethyl-l,5-heptadien-3-ol acetate (24, 25) and in 1981, we identified the pheromone of the citrus mealybug, Planococcus citri (Risso), as (lR-cis)-(+)-2,2-dimethyl-3-(l-methylethenyl)cyclobutanemethanol acetate (26). Both of these pheromones have been synthesized and are currently being used as baits in monitor traps in California and Texas. These compounds are more volatile than the pheromones for most other insects and therefore formulations for controlled release need to be modified from those described earlier. 

The first step involves the formation of a-bonded tetravinyltitanium. Homolytic cleavage produces vinyl radicals and an active titanium atom. Two moles of 1,3-butadiene can be formed, which constitute the first coupling. The 1,3-butadiene thus produced is free to form a 7r-complex with the active titanium atom. Further cleavage of this unstable complex results in the formation of the isolable products, primarily 4-vinylcyclo-hexene-1 as well as some 2,6-octadiene, 3-methyl-l,5-heptadiene, and 3-methyl-l,4,6-heptatriene. Many other interesting catalysts at the atomic level have been reported and are reviewed (5, 7, 8). 

Geraniolene itself is 2,6-dimethyl-l,5-heptadiene (164), and has been made readily by reaction of isoprene with isobutylene in the presence of phosphomolybdic acid, this occurring with 69% selectivity and 56% conversion of Isoprene. 

The [2,3]-rearrangement of amine iV-oxides was utilized in an efficient S5mthesis of 2,6-dimethyl-l,5-heptadien-3-ol acetate 61, a pheromone of the insect Pseudococcus comstocki tScheme lS.12id Dimethylpyridine 55 was converted in two steps into silylated piperidine 56, which was oxidized with m-CPBA to generate cyclic amine A-oxide 57. Sila-Cope elimination furnished O-silylhydroxylamine 58, which was methylated and desilylated in the presence of Mel and CsF to yield acyclic amine A-oxide 59. Heating this ammonium zwitterion facilitated the [2,3]-Meisenheimer rearrangement to O-allylhydroxylamine 60, which was transformed to the desired pheromone 61 in three steps. 

Scheme 15.12 Synthesis of the pheromone 2,6-dimethyl-l,5-heptadiene-3-ol acetate.

Geranic Acid (2 6-Dimethyl-l 5-heptadiene-1-caiboxylie acid and 2 5-dimethyl-l 6-hepta-diene-l-carbozylic acid)... 

Dimethyl-l,5-heptadiene [6709-39-3] Table 1. Fit with estimated B coefficient for 3... 

Trimethyl-l,5-heptadiene [35387-63-4] Table 1. Experimental value with uncertainty. 

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