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.

trans-4,5-Diamino-cyclopent-2-enones (CP) are usually prepared by Lewis acid-catalyzed condensation of furfural and a secondary amine in an organic solvent. The reaction proceeds through the formation of a Stenhouse salt (SS) intermediate followed by an electrocyclization reaction to afford the desired CP. Herein, we described the use of Cu(OTf) as a very efficient catalyst for the synthesis of CP in water at room temperature. Furthermore, the mild reaction conditions, catalyst reusability, and outstanding functional group tolerance suggest that this CP platform can be further used in chemical biology.

The preparation of high value‐added chemicals from renewable resources is a crucial approach towards a sustainable economy. One prominent alternative to the production of petroleum‐based chemicals from fossil resources is through the sequential Diels‐Alder/aromatization reactions of biomass‐derived furan platforms. This Concept is focused on the recent boom in bio‐based furan DA strategies for aromatization of bio‐based platform chemicals, particularly that of furfurals, ranging from indirect use and activation strategies to recent examples of direct DA reaction of these electron‐withdrawing biomass‐derived furans.

The lack of thermal and storage stability and occurrence of side reactions during the processing of 5-hydroxymethylfurfural (5-HMF) limits its potential as biorenewable platform molecule. The addition of small amounts of the readily available sodium dithionite has a remarkable effect on promoting the stability of 5-HMF and inhibiting side reactions, thus helping to circumvent such limitations. The addition of sodium dithionite led to improvements in thermal stability (120 °C, 4 h, neat; 100 % vs. 37 %), under distillation (yield: 85 % vs. 52 %), and in a wide range of reactions, including 5-HMF synthesis under biphasic conditions (yield: 98 % vs. 67 %; purity: 92 % vs. 83 %) and 5-HMF transformations, such as Knoevenagel condensation with Meldrum's acid (yield: 96 % vs. 74 %), Cannizaro reaction (yield: quantitative vs. 83 %), and condensation with primary diamines to give pyridinium salts (yield: 88 % vs. 60 %).

3A5AF, a biomass derived furan obtained from chitin, is used as a diene in the Diels–Alder reaction with maleimides. This allows the incorporation of bio-based nitrogen into the final products, a challenge unmet by commonly used furanics.