Mono activity

While doubly activated dienophiles gave moderate to good yields under thermal conditions (Table 11), mono activated alkenes such as cyclohexenone (123) failed to react at temperatures up to 150 °C but underwent cycloaddition under Lewis-acid catalysis even if with poor yields (Table 12, entries 1-3) [32],... 

Cycloadditions onto Methylene- and Alkylidenecyclopropane Derivatives Table 12. Cycloaddition of 112 to mono activated dienophiles... 

A synthetically useful procedure for the one-pot conversion [1] of vicinal diols into epoxides involves selective mono-activation of one hydroxyl group (by reaction with 1 equiv. of tosyl... 

Lithium benzeneselenolate reacted with acetylcyclopropane (5, R = H R = Me) and other mono-activated cyclopropanes to ring-opened products 6 with a benzeneselanyl substituent at the terminal carbon atom. ... 

Table 11.9. Diels-Alder Adducts of Furan Derivatives and Mono-Activated Dienophiles...

In contrast, the europium(fod)3 catalyzed Diels-Alder reactions of the mono-activated olefins 102a and 102b led to mixtures of products (Fig. 3.28). After refluxing for 2 h in o-dichlorobenzene ether 102a gave a 6 1 ratio of the pyridine 103a and the 3-hydroxypyridine 104a, respectively, in 35% overall yield. The... 

Just taking a quick look at the different chapters, one can realize which areas of each field are mature and which can evolve immediately. Although it is very difficult to venture a general trend for the whole area, we could emphasize that there is not a tmly enantioselective version for the mono-activated hydrogen autotransfer reaction. The use of first-row transition metals is almost an unexplored Blue Ocean , in all aspects. Furthermore, the possible impact of green neoteric solvents, including deep eutectic mixtures, supercritical fluids, and bio-based solvents, on the hydrogen transfer process is definitely unknown. 

Using Lewis acid BF3 Et20 as catalyst enhances the yield of oxidative cycloaddition of thiophenes with mono-activated dienophiles, a reactitMi that gives poor yields of cycloaddition products under uncatalyzed conditions [13],... 

Scheme 18.12 Enantioselective intermolecular Stetter reactions of mono-activated acceptors.

However, two problems posed by these results are the required aldol condensation onto a mono-activated methyl rather than the usual doubly activated methylene and the incorporation into skyrin implies loss of ketide oxygen and subsequent reoxidation of the same, and now, unactivated position, which seems highly inefficient biosynthetically. Oxygen-18 studies to confirm the origins of... 

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