Bicyclo heptadienes synthesis

Interestingly, zirconacyclopentane 246 formed by the reaction of 1,6-heptadiene with the Zr complex has the firms ring junction mainly [108]. It should be noted that the preparation of the trans ring junction in the bicyclo[3.3.0]octane system by other means is difficult. Carbonylation of 246 affords trans-fuzed bicyclo[3.3.0]octanone 247 [109,111]. The diacetoxy compound 248 is obtained by oxidative cleavage of 246. Protonation affords the frans-dimethylcyclopentane skeleton. Similar reactions occur with 1,6-enynes, and Pauson Khand-type cyclopentenone synthesis is possible by carbonylation. 

Synthetic applications of the reaction are somewhat limited as the highly reactive biradicals and radical pairs tend to undergo reactions that compete with C—C bond formation. As in previous cases, the reaction may have synthetic value for the synthesis of strained structures involving small rings. For example, the preparation of the simplest [2]-ladderane 55 by photodecarbonylation of bicyclo[3.2.0]heptan-3-one 54 gave the bicyclic structure in 5% yield with a ring-opened 1,5-heptadiene being the dominant product (Scheme 2.14) [41]. 

The chiral Diels-Alder adduct 19 is a versatile intermediate for the synthesis of many chiral bicyclo[2.2.1]heptadienes, because the tri-n-butylstannyl group can be replaced by halogen or a wide variety of carbon appendages, the latter by use of either copper-mediated or palladium-catalyzed cross-coupling reactions. For example, as shown in Eq. (34), reaction of 19 with A-iodosuccinimide produced the iodo aldehyde 12 in 92 % yield. Coupling of 12 with ( )-/ -styryl-tri-n-butylstannane and either 1.5 equiv. copper(I) 2-thiophenecarboxylate (CuTC) or catalytic PdCl2(CH3CN)2 afforded the triene aldehyde 20 [34]. 

An important achievement in the research on insecticides of the diene group was the development of 1,2,3,4,10,10-hexachloro-l,4,4a,5,8,8a-hexahydro-ex o-1,4-e/i(/o-5,8-dimethanonaphthalene (aldrin, HHDN, 51) (Lidov, 1953). The preparation of the compound involves two Diels-Alder reactions. First, bicyclo-(2,2,l)-2,5-heptadiene (52) is prepared by the diene synthesis of acetylene and... 

Methoxy-3,6-bicyclo[3,2,0]heptadien-7-one is readily available from the photo-chemically induced valence tautomerism and skeletal reorganization of the methyl ether of tropolone. The double bond of the ap-unsaturated ketone can be selectively reduced to give (375). Ozonolysis of (375) in methanol-methylene chloride at low temperature, followed by treatment of the ozonide with liquid sulphur dioxide, gives the substituted cyclopentanone (376X which has been used in yet another prostaglandin synthesis. ... 

The Cu(I)-catalyzed photocycloaddition of l,6-heptadien-4-ol 59 (Scheme 18) was employed by Lai and co-workers for the synthesis of the sesquiterpenes robustadials for which the structures 61 were proposed. The bicyclo[3.2.0]heptane 60 obtained from this reaction was converted to three of the four... 

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