i) Doubly electrophilic reagents

They are reagents that have two positions with strong positive polarity to which nucleophiles attack. These reagents form cycles when confronted with others that are doubly nucleophilic. These are dicarbonyls, alpha, beta-unsaturated, alpha-halogenated carbonyls.

doubly electrophilic reagents

ii) Doubly nucleophilic reagents

They are reagents that have two nucleophilic centers, generally atoms with lone pairs, although they also have double nucleophilic character, triple bonds and aromatic rings.

doubly nucleophilic reagents

iii) Electrophilic reagents - nucleophiles.

In the synthesis of rings we can also use reagents that combine both electrophilic and nucleophilic centers.

nucleophilic electrophilic reagents