Subsequent Cycloadditions to -double Bonds

What is the influence of the structural and electronic properties of the precursor adducts on the product distribution Analysis of various experimental and calculated [6,6] monoadduct structures shows that the bond length alternation between [5,6]-and [6,6]-bonds is preserved [1]. Significantly, independently of the nature of the 

Positional relationship C,(COOMe), Cs2(phenyl)2 C,o(NCOOMe)2 Q,(COOMe)2(NCOOMe) 

For example, adduct 12 was formed from e-4, trans-3-6 and trans-2-7. Consequently, it must involve these three positional relationships. Therefore, its structural assignment is unambiguous. Similarly, various trisadducts carrying C2-symmetrical bis(oxazoline) addends could be isolated and structurally assigned [19, 20]. The regioselectivities of these cyclopropanations strongly depend on the precursor bisadduct. Whereas, for example, all possible trisadducts 9,10, 12,14 that can be obtained from trans-3-6 were formed in about equal amounts the cyclopropanation of trans-4-5 is more selective. Among the four isolated isomers 10 was the most abundant. The fifth isomer, with a Cj -symmetrical tmns-4, trans-4, trans-4- addition pattern, was not found. 

Only three of the six possible trisadducts were obtained upon cyclopropanation of e-4. Especially, the adducts with the addition patterns e,e,-trans-l (I) and e,e,-trans-1 (11) did not form [20]. Access to corresponding adducts requires trans-1 precursors and/or tether strategies (Section 10.3.3). Although the relative yield of e,e,e-8 constitutes about 35-40% of the trisadducts formed and the yield of e,trans-3,trans- 2-12 is higher, the preferred mode of addition is e relative to the 

A CgoHg isomer with a Dj symmetrical all trans-3 addition pattern was found as the preferred adduct upon the hexahydrogenation of Cjq via Zn-Cu acid reduction [21]. 

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