Photo-Fries-type rearrangement of cyclic enamides. An efficient route to structurally diverse five-membered enaminones

Abstract

A simple, efficient and user-friendly protocol for the preparation of structurally diverse enaminones from enamides has been developed. The strategy is based on a photo-induced intramolecular Fries-type rearrangement. The photochemical...

Remotely controlled flow photo-Fries-type rearrangement of N-vinylazetidinones: an efficient route to structurally diverse 2,3-dihydro-4-pyridones

“…Our previous paper describes a detailed plan for reactor construction. 54 In optimization studies N -vinylazetidinone 3a was used as a model substrate. All optimization experiments were carried out as batch processes using degassed solvents and under an argon atmosphere.…”

“…Very recently we have presented details of how to build an easy-to-operate photoreactor for around 150 euros. 54 Herein, we present how this system, at a low cost and using equipment available in most laboratories, can be expanded to continuous flow with real-time monitoring.…”

Diversity-oriented synthesis of medium-sized cyclophanes via the photo-fries rearrangement of N-aryl lactams

“…The construction of the reactor is described in detail in a previous paper. 59 The photochemical reactions were performed with a UV-C light source ( λ max 254 nm) in two solvents, methanol and cyclohexane. Irradiation of β-lactam 3a in methanol did not lead to the desired product.…”

“…A plausible mechanism proposed for this reactivity involves homolytic cleavage of the amide bond by irradiation with 254 nm light (Scheme 5). 59,61,62 The resulting biradical II can then either recombine to reform the starting material I or combine with either of the two possible resonance structures III and IV to generate imines V and VI , respectively. Subsequent rearomatization of V and VI give the observed ortho - and para -substituted products VII and VIII .…”

Chemoselective Transformations of Amides: An Approach to Quinolones from β-Amido Ynones

“…Normally, the major transformation of amides was initiated by the addition of highly active organometallic reagents and heteroatom nucleophile anions, such as organolithiums, Grignard reagents, and amino anions, to their carbonyl C 2 sites to intermediate I and deamination (eqs 1 and 2) . Alternatively, the carbonyl C 2 sites of amides can be attacked by a nucleophilic anion to achieve the selective C–O bond cleavage in the synthesis of enamines, such as Wittig reaction, Tebbe olefination, and other olefination reactions (eq 3) . However, these reactions required at least equivalent nucleophilic reagents and produced equivalent byproducts, along with harsh conditions, such as metal participation, high temperature, etc.…”