Eucalyptol as bio-based solvent for Migita–Kosugi–Stille coupling reaction on O,S,N-heterocycle

Synthesis of 4-(Phenylamino)quinazoline-2(1H)-thiones Using Green Solvents

Given the importance of quinazolines and quinazolinethiones in therapeutic and Food and Drug Administration (FDA)-approved molecules, we thought interesting to consider their synthesis in green solvents. We have shown that obtain 4-(arylamino)quinazoline-2-(1H)-thiones and 4-(arylamino)pteridine-2-(1H)-thiones analogues was efficient in green solvents derived from biomass, especially eucalyptol. Although reaction times are somewhat long to achieve good yields, the products were obtained by simple filtration. This considerably limited the loss of atoms due to the use of large quantities of solvents for purification on silica gel columns, and makes our route a sustainable one.

Sabinene: A New Green Solvent Used in the Synthesis of Thiazolo[5,4-b]pyridines by Thermal or Microwave Activation

Following the work already carried out in our laboratory on eucalyptol, a new green solvent derived from biomass, we are now looking at sabinene as another new green solvent. Sabinene is also derived from biomass, has no known toxicity and can be recycled by distillation. We have shown that it can be used as it is or distilled to synthesize thiazolo[5,4-b]pyridine heterocycles by thermal activation or microwave irradiation. This new solvent was compared with various conventional and green solvents. The conditions were optimised to enable us to carry out the syntheses in satisfactory yields, and we were able to show that sabinene, a natural bicyclic monoterpene, could be used effectively as a solvent.

Antioxidant Effects of Catechins (EGCG), Andrographolide, and Curcuminoids Compounds for Skin Protection, Cosmetics, and Dermatological Uses: An Update

Here we have chosen to highlight the main natural molecules extracted from Camellia sinensis, Andrographis paniculata, and Curcuma longa that may possess antioxidant activities of interest for skin protection. The molecules involved in the antioxidant process are, respectively, catechins derivatives, in particular, EGCG, andrographolide, and its derivatives, as well as various curcuminoids. These plants are generally used as beverages for Camellia sinensis (tea tree), as dietary supplements, or as spices. The molecules they contain are known for their diverse therapeutic activities, including anti-inflammatory, antimicrobial, anti-cancer, antidiabetic, and dermatological treatment. Their common antioxidant activities and therapeutic applications are widely documented, but their use in cosmetics is more recent. We will see that the use of pharmacomodulated derivatives, the addition of co-antioxidants, and the use of various formulations enable better skin penetration and greater ingredient stability. In this review, we will endeavor to compile the cosmetic uses of these natural molecules of interest and the various structural modulations reported with the aim of improving their bioavailability as well as establishing their different mechanisms of action.

Replacement of Less-Preferred Dipolar Aprotic and Ethereal Solvents in Synthetic Organic Chemistry with More Sustainable Alternatives

Dipolar aprotic and ethereal solvents comprise just over 40% of all organic solvents utilized in synthetic organic, medicinal, and process chemistry. Unfortunately, many of the common "go-to" solvents are considered to be "less-preferable" for a number of environmental, health, and safety (EHS) reasons such as toxicity, mutagenicity, carcinogenicity, or for practical handling reasons such as flammability and volatility. Recent legislative changes have initiated the implementation of restrictions on the use of many of the commonly employed dipolar aprotic solvents such as dimethylformamide (DMF) and N-methyl-2-pyrrolidinone (NMP), and for ethers such as 1,4-dioxane. Thus, with growing legislative, EHS, and societal pressures, the need to identify and implement the use of alternative solvents that are greener, safer, and more sustainable has never been greater. Within this review, the ubiquitous nature of dipolar aprotic and ethereal solvents is discussed with respect to the physicochemical properties that have made them so appealing to synthetic chemists. An overview of the current legislative restrictions being imposed on the use of dipolar aprotic and ethereal solvents is discussed. A variety of alternative, safer, and more sustainable solvents that have garnered attention over the past decade are then examined, and case studies and examples where less-preferable solvents have been successfully replaced with a safer and more sustainable alternative are highlighted. Finally, a general overview and guidance for solvent selection and replacement are included in the Supporting Information of this review.

Eucalyptol, an All-Purpose Product

Eucalyptus plants have attracted the attention of researchers and environmentalists worldwide because they are a rapidly growing source of wood and a source of oil used for multiple purposes. The main and the most important oil component is 1,8-cineole (eucalyptol: 60–85%). This review summarizes the literature reported to date involving the use of 1,8-cineole for the treatment of disorders. Additionally, we describe our efforts in the use of eucalyptol as a solvent for the synthesis of O,S,N-heterocycles. Solvents used in chemistry are a fundamental element of the environmental performance of processes in corporate and academic laboratories. Their influence on costs, safety and health cannot be neglected. Green solvents such as bio-based systems hold considerable additional promise to reduce the environmental impact of organic chemistry. The first section outlines the process leading to our discovery of an unprecedented solvent and its validation in the first coupling reactions. This section continues with the description of its properties and characteristics and its reuse as reported in the various studies conducted. The second section highlights the use of eucalyptol in a series of coupling reactions (i.e., Suzuki–Miyaura, Sonogashira–Hagihara, Buchwald–Hartwig, Migita–Kosugi–Stille, Hiyama and cyanation) that form O,S,N-heterocycles. We describe the optimization process applied to reach the ideal conditions. We also show that eucalyptol can be a good alternative to build heterocycles that contain oxygen, sulfur and nitrogen. These studies allowed us to demonstrate the viability and potential that bio solvents can have in synthesis laboratories.

Demonstration of Green Solvent Performance on O,S,N-Heterocycles Synthesis: Metal-Free Click Chemistry and Buchwald-Hartwig Coupling

The development of new and greener approaches to organic synthesis has been a trend in recent years. Continuing the latest publications of our team, in this work, we demonstrate the efficiency of three solvents: eucalyptol (1,8-cineole), cyclopentyl methyl ether (CPME), and 2-methyltetrahydrofuran (2-MeTHF) for the synthesis of O,S,N-heterocyclic compounds.

Eucalyptol: A Bio-Based Solvent for the Synthesis of O,S,N-Heterocycles. Application to Hiyama Coupling, Cyanation, and Multicomponent Reactions

We report here the use of eucalyptol as a bio-based solvent for Hiyama coupling, cyanation, and multicomponent reactions on O,S,N-heterocycles. These heterocycles were chosen as targets or as starting materials given their biological potential; they play an important role in therapeutically active compounds. Once again, eucalyptol proved to be a credible and sustainable alternative to common solvents.

Laser synthesis: a solvent-free approach for the preparation of phenylthiazolo[5,4-b]pyridine derivatives

We describe here a rapid and straightforward solvent-free method to access phenylthiazolo[5,4-b]pyridines using a Nd-YAG laser NANO-NY81-10 (λ = 355 nm, 10 Hz pulse frequency; 8 ns pulse duration).