Deca-2,8-diene stereoselectivity

A similar rearrangement was used in a stereoselective synthesis of (if, )-3,7-dimethyT2,6-deca-diene-l,10-diol (pheromone of the queen butterfly) in six steps from gcraniol (Table 3, entry 16)310. Use of 2-methoxy-l,3-butadienes and related compounds (e.g., unsaturated acetals311) allows an iterative Claisen rearrangement by reduction of the resulting enone28,309. 

In the case of electrophilic addition, the reactions of tricyclic dienes 1 with several electrophilic reagents have been investigated.1 7 Interestingly, some of these compounds undergo addition reactions with remarkable syn stereoselectivity. For example, the reaction of dimethyl tricy-clo[4.2.2.02,5]deca-3,9-diene-7,8-dicarboxylate with iodine azide solution, prepared in situ from an excess of sodium azide and iodine monochloride, in acetonitrile at — 5 C provided the. yyn-4-azido-3-iodo derivative 2 (Table 1) in 90% yield.1,2,4,6 The formation of the 5,>,n-4-azido-3-iodo derivative 2 is thought to be the first example of a syn addition of iodine azide to an alkene.1,2 The formation of the syn-product is best explained by the twist strain theory,8 according to which the syn transition structure A is favored over the an/7-coplanar transition structure B.1... 

Alkenylboron compounds couple with the representative organic halides or triflates (Scheme 28). Hexaalkylbenzene was synthesized by sixfold alkenylation (55) of hexabromobenzene followed by catalytic hydrogenation of the double bonds 11521. The reaction of 1-alkenylborane with 1-bromo-l-alkyne stereose-lectively provided ( )-enyne (56) which was then converted into ( ,Z)-hexa-deca-10,12-dienal, a sex pheromone of the melonworm 11531. Due to the difficulty of purification of a geometrical mixture, the stereoselective synthesis is critical for such dienes or trienes. The PGEi derivatives (57) were synthesized... 

This model also predicts that selectivity for the tranr-fused cycloadducts in nonatriene (n = 0) or deca-triene (n = 1) cyclizations should increase as size of the coefficients at C 2)IC S + n) are increased relative to those at C(l)/C(9 + n), that is, as the polarization of the dienophile or diene is increased. Tables 1 and 2 summarize results of intramolecular Diels-Alder reactions that provide a test of this propo-gai.24.25 it ig tiiat an electron-releasing Et N group at C(9) of the nonatrioioate system leads to a substantial increase in selectivity for the trans-fased product (compare entries 4-6, Table 1). Increased trans stereoselectivity also occurs with C(9)-alkoxy-substituted nonatrienes. A similar effect... 

Most of the available data on stereoselectivity of metathesis of acyclic olefins relate to cis- and trans-2-olefins, but it is convenient here also to consider some results for propene, but-l-ene, and pent-l-ene, also cis,cis- and trans,fra i-deca-2,8-diene. 

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