Iterative Wittig olefination

A. Dondoni, A. Marra, M. Mizuno, and P. P. Giovannini, Linear total synthetic routes to [3-d-C-( 1.6)-linked oligoglucoses and oligogalactoses up to pentaoses by iterative Wittig olefination assembly, J. Org. Chem., 67 (2002) 4186—4199. 

Dondoni, A, Kleban, M, Zuurmond, H, Marra, A, Synthesis of (1 — 6)-C-oligogalactosides by iterative Wittig olefination. Tetrahedron Lett., 39, 7991-7994, 1998. 

Dondoni, A., Marra, A., Mizuno, M., Giovannini, P. P. Linear Total Synthetic Routes to -D-C-(1,6)-Linked Oligoglucoses and Oligogalactoses up to Pentaoses by Iterative Wittig Olefination Assembly. J. Org. Chem. 2002, 67,4186-4199. 

A multiple one-pot iterative asymmetric hydroformylation-Wittig olefination was realized with a single catalyst loading (Scheme 5.137) [26]. Noteworthy, after each run, depressurization and injection of the allyl-substituted Wittig reagent was necessary in order to avoid the undesired hydroformylation of the Wittig ylide. In this manner, the dimer and the trimer of 4-hydroxyvalerate were prepared. 

Scheme 5.137 Synthesis of dimer and trimer of 4-hydroxyvalerate by iterative hydroformylation-(Wittig olefination) reaction using a single catalyst.

The most obvious method to install the C1-C2 alkene of a dendralene is an olefination reaction (Scheme 1.19), but it has seen very little use, because of the propensity of 2-carbonyl-1,3-butadiene derivatives to undergo rapid Diels-Alder dimerization [81]. In fact, the only successful uses of 2-carbonyl-1,3-butadienes in such processes feature substrates stabilized by 1,1-disubstitution and a 4Z substituent. Such an example is the iterative formylation/olefination sequence reported by Yoshida and coworkers (Scheme 1.20) [82]. A selective, single electrophilic formylation followed by a Wittig reaction gave hexa-substituted... 

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