The Formation of Cyclic Ketones by IntramolecularAcylation

Abstract

The cyclizations of gamma‐phenylbutyric acid (I) to tetralone‐1 (II) and of beta‐phenylpropionic acid (III) to hydrindone‐1 (IV) exemplify a type of intramolecular acylation which has served as an important tool in the synthesis of polycyclic hydroaromatic and aromatic compounds, Such ring closures have been effected by a variety of methods, generally involving either the direct cyclodehydration of the acids or the cyclodehydrohalogenation of the acid chlorides by an intramolecular Freidel‐Crafts reaction. This chapter presents a discussion of these methods and the various problems involved in the formation of cyclic ketones by the ring closure of aryl‐substituted aliphatic acid.

Non-Conventional Methodologies in the Synthesis of 1-Indanones

“…In fact, the “one-step reaction” produces water as the only by-product while the “two-step reaction” generates a large amount of toxic and corrosive compounds. Nevertheless, direct cyclization usually requires an excess of protic acids (even as solvents) such as sulfuric acid, hydrogen fluoride [30], polyphosphoric acid [31], methanesulfonic acid (MSA) [32], a mixture of MSA and P 2 O 5 [33], or Lewis acids such as AlCl 3 and SnCl 4 [30]. Some lanthanide triflates, in particular Tb(OTf) 3 , were reported to be useful catalysts for the dehydrative cyclization of 3-arylpropionic acids to form 1-indanones [34] in o -chlorobenzene at very high temperatures.…”

“…As mentioned above, the examples of direct intramolecular Friedel-Crafts acylation of 3-arylpropionic acids to produce 1-indanone derivatives are very far from satisfying many green chemistry principles since they are performed under extremely drastic experimental conditions, such as elevated reaction temperatures (250 °C in chlorobenzene) and require very long reaction times [23,24,25,26,27,28,29,30,31,32,33,34]. In light of the enormous diffusion and application of non-conventional techniques in the implementation of synthetic green processes [35,36,37,38], and our own experience in this field [39,40,41,42,43,44], we decided to explore the use of microwave irradiation (MW), high-intensity ultrasound (US) and high-pressure conditions to develop a greener synthesis of 1-indanone derivatives via the intramolecular Friedel-Crafts acylation of 3-arylpropionic acids.…”