Synthesis and Applications of Stenhouse Salts and Derivatives

Abstract

In recent years, Stenhouse salts have attracted much attention as intermediates for the synthesis of cyclopenten-2-enones. This Minireview aims to present an overview of the methods for preparation, further transformation and applications of Stenhouse and Stenhouse-like salts. In this context, the Piancatelli rearrangement and its variants, and the recently reported donor-acceptor Stenhouse salts (DASA) will be addressed. The photophysical properties of DASA and its applications in colorimetric detection of amines, functionalization of polymers for detection of heat and nerve agents, photolithography and orthogonal photoswitching systems are discussed.

Solvent Effects on the Actinic Step of Donor–Acceptor Stenhouse Adduct Photoswitching

“…Donor-acceptor Stenhouse adducts (DASAs,F igure 1a) were introduced in 2014 [17,18] and feature important advantages as compared to traditional photoswitches,i ncluding visible light responsiveness [11,19,20] and negative photochromism. [21] Moreover,t heir modular architecture [22] allows for afine-tuning of properties. [23] First-generation DASAs (1 and 2,F igure 1a) [17,18] are based on dialkylamine donors,whereas second-generation DASAs (3) [24,25] employ secondary anilines leading to bathochromically shifted spectra.…”

Direct Conversion of Activated 5‐Hydroxymethylfurfural into δ‐Lactone‐Fused Cyclopentenones

“…Moreover, the use of furan derivatives, such as furfurals and furfuryl alcohols, as starting materials is a very elegant strategy for the highly selective synthesis of trans ‐4,5‐disubstituted CPs, as reported by the groups of Piancatelli, Batey, and Read de Alaniz (Scheme a) . The generally accepted mechanism involves the formation of a Stenhouse adduct (SA) by furan ring opening followed by an electrocyclization reaction to yield the corresponding 4,5‐functionalized CP . Recent advances towards the use of SA in the field of materials chemistry led to the development of donor–acceptor Stenhouse adduct (DASA)/CP systems (Scheme b) .…”

“…Recent advances towards the use of SA in the field of materials chemistry led to the development of donor–acceptor Stenhouse adduct (DASA)/CP systems (Scheme b) . These systems have been extensively explored for their properties as photoswitches for a variety of applications in materials chemistry, such as in colorimetric detection of amines and nerve agents, adsorption in photoresponsive polymers and orthogonal photoswitching systems . DASAs are prepared from activated furfurals, such as the product obtained from the Knoevenagel condensation between furfuraldehyde and Meldrum's acid.…”

“…Our study focused on upgrading this platform in the context of synthetic and medicinal chemistry. The valorization of biomass intermediate HMF was achieved through the synthesis of novel CP scaffolds by taking advantage of knowledge in materials chemistry; a strategy for furfural activation used in the synthesis of DASA photoswitches.…”

Synthesis of Bridged Tetrahydrobenzo[b]azepines and Derivatives through an Aza‐Piancatelli Cyclization/Michael Addition Sequence

“…[6] Thelimited output for these challenging molecules might find its origins in the difficulty to prepare these frameworks,w hich has hampered any real study on their potential bioactive properties.T herefore,w eb elieved that designing ag eneral approach to access these synthons could make ad ifference,n ot only by boosting the interest in them from the pharmaceutical industry but also,more generally,by filling avoid in the synthesis of N-heterocycles.T oaccomplish this objective,w ew ondered whether the aza-Piancatelli cyclization could be exploited to close this gap. [7] Over the past few years,t his Nazarov-type electrocyclization [8] has been at the heart of our research program, granting rapid access to privileged building blocks such as 4-aminocyclopentenones,c yclopenta [b]pyrroles,a nd cyclopenta- [b]piperazinones from readily available 2-furylcarbinols. [9] In that respect, by taking ac lose look at the compounds generated during the cyclization, we reasoned that the introduction of an itrogen functionality on the carbinol moiety might be the answer to this issue.I np ractice,o nce the aza-Piancatelli cyclization is complete (first step), adding ab ase to the reaction mixture would be sufficient to trigger aM ichael addition (second step) and assemble tetrahydrobenzo [b]azepines in ao ne-pot sequence.…”