Dienylic ethers, cycloaddition

Synthesis of functionalized aryloxy 1,3-butadienes and their transformation to dienyl ethers via Diels-Alder cycloaddition reactions [136]... 

Cycloaddition of Butyl Glyoxylate to ttans-Dienyl Ether 4... 

David, S, Eustache, J, Lubineau, A, Cycloaddition as a possible path to disaccharide synthesis stereochemical course of the reaction of butyl glyoxylate with a chiral, protected dienyl ether of glucose, J. Chem. Soc. Perkin. Trans. 1, 2274-2278, 1974. 

Significant improvement in the synthesis of disaccharides by cycloaddition may be achieved by reaction of diethyl mesoxalate with the dienyl ethers of protected sugars. This more active dienophile adds to both cis- and trans-ethers, unlike compounds hitherto reported, and more efficient utilization of the protected starting sugar is possible. 

David s group have applied their diene approach to disaccharides to the synthesis of kasuganobiosamine (30). Cycloaddition of the dienyl ether (31) with menthyl glyoxylate gave a glycal which was converted to the glyceno-sidulose (32) which, in turn, led to (30) by sequential hydrazoic acid addition, oximation, reduction, and deblocking. ... 

The [2 + 2] cycloaddition of the propynyl tungsten complex (12b) has been found to be stereospecific with the cis and trans isomers of eAyl prc nyl ether." ITie reaction with c/s-propenyl ethyl ether gave rise to the cyclobutenyl complex (18), in addition to a minor amount of the ring-opened dienyl carbene complex (19). The stereochemistry about the double bonds in the dienyl complex (19) revealed that it was derived from a thermal electrocyclic conrotatory ring opening of the c/s-cyclobutenyl carbene complex (18) and thus the stereochemistry is completely retained in this cycloadditirxi. In support of this analysis it was found that cyclobutenyl complex (18) could be thermally opened to the dienyl complex by heating in an inert solvent at 50 C. In the cycloaddition of the propynyl complex (12) with trans-... 

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