Dedicated to Professor Yashwant D. Vankar on the occasion of his 70th birthday
Abstract
Cyclic ketones, anhydrides, lactams and lactones are a particular class of molecules that are often used in synthesis, wherein their electrophilic properties are leveraged to enable facile Friedel–Crafts ring openings through nucleophilic attack at the carbonyl sp2 centre. The use of electron-rich alkoxybenzenes as nucleophiles has also become important since the discovery of the Friedel–Crafts reaction. As a result, various isomeric alkoxybenzenes are used for preparing starting materials in target-oriented syntheses. This review covers the instances of different alkoxybenzenes that are used as nucleophiles in ring-opening acylations with carbonyl-containing cyclic electrophiles, for the construction of important building blocks for multistep transformations. This review summarizes the ring-opening functionalization of three- to seven-membered molecular rings with alkoxybenzenes in a Friedel–Crafts fashion. Sometimes the rings need subtle or considerable activation by the help of Lewis acid(s), followed by nucleophilic attack. This review is aimed to be a summary of the important acylations of electron-rich alkoxybenzenes by nucleophilic ring-opening of cyclic molecules. The works cited employ a wide range of conditions and differently substituted substrates for target-oriented syntheses.
1 Introduction and Scope
2 Arenes for Acylative Ring Opening
2.1 Three-Membered Rings: Ring Opening of Oxirane-2,3-dione
2.2 Four-Membered Rings
2.2.1 Ring Opening of Cyclobutanones
2.2.2 Ring Opening of β-Lactams
2.2.3 Ring Opening of β-Lactone
2.3 Five-Membered Rings
2.3.1 Ring Opening of Phthalimides
2.3.2 Ring Opening of γ-Lactones
2.3.3 Ring Opening of Anhydrides
2.4 Six-Membered Rings
2.5 Seven-Membered Rings
3 Conclusion
Key words
Friedel–Crafts acylation - methoxybenzene - dimethoxybenzene - trimethoxybenzene - Lewis acid - β-lactam - β-lactone
