Diels-Alder reaction of fulvenes with N-(3,5-dichlorophenyl)-maleimide

An overview of the cycloaddition chemistry of fulvenes and emerging applications

“…Pentafulvenes show dual capabilities in DACs, with documented examples of them functioning as both dienes and dienophiles [55,114,150–151 154,159,174–176 227–229]. The exact nature of the fulvene moiety is dependent mostly on its substituents (e.g., EWG or EDG) relative to the other reactants [6,42,45,67,103,153,230].…”

“…The exact nature of the fulvene moiety is dependent mostly on its substituents (e.g., EWG or EDG) relative to the other reactants [6,42,45,67,103,153,230]. Maleimides (including maleic anhydride) [55,71,92,96,150,176–177 179–184 186,192,229,231], dimethyl acetylenedicarboxylate (DMAD) and p -benzoquinone [60,150,159,164,175,211] derivatives [174,183,200,229] are often used as the complementary dienophiles (Scheme 14, reaction pathways (i), (ii) and (iii), respectively), as well as mono- and disubstituted acetylene derivatives, such as methyl propiolate [229] and dibenzoylacetylene [150].…”

“…Regardless of the role of the fulvene moiety, the DAC is generally conducted in organic solvents at room temperature and under an inert atmosphere to prevent unwanted oxidations [24,55,94,114,150,152,159,166,172,174,176,183,186,227,229]. There are very few papers reporting the aforementioned reaction occurring in aqueous conditions [175] most likely as a result of the poor solubility of fulvene derivatives in water [175].…”

“…Although the stereochemistry of DACs can usually be predicted by the ‘endo rule’ [92,176,229,232], there are some exceptions, particularly when sterically-demanding fulvenes, such as norbornyl-fused fulvenes [229] or adamantilydenefulvene [174] are involved. In the literature, many cycloaddition reactions have been conducted with dimethylfulvene [52,97,106,118,133–134] or diphenylfulvene [20,103,114,133,163,180].…”

“…In the literature, many cycloaddition reactions have been conducted with dimethylfulvene [52,97,106,118,133–134] or diphenylfulvene [20,103,114,133,163,180]. In each instance, the endo stereochemistry of the cycloadduct is dominant [91,176,180], indicating that the fulvene substituents in the exocyclic C6 position are too distal to impact the stereoselectivity [76,229].…”