Although fire is now rarely used in synthetic chemistry, it was not until Robert Bunsen invented the burner in 1855 that the energy from this heat source could be applied to a reaction vessel in a focused manner. The Bunsen burner was later superseded by the isomantle, oil bath, or hot plate as a source for applying heat to a chemical reaction. In the past few years, heating and driving chemical reactions by microwave energy has been an increasingly popular theme in the scientific community. This nonclassical heating technique is slowly moving from a laboratory curiosity to an established technique that is heavily used in both academia and industry. The efficiency of "microwave flash heating" in dramatically reducing reaction times (from days and hours to minutes and seconds) is just one of the many advantages. This Review highlights recent applications of controlled microwave heating in modern organic synthesis, and discusses some of the underlying phenomena and issues involved.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.200400655

Controlled microwave heating in modern organic synthesis.

6.4. Polyynes 3123 6.5. Using R-Hydroxy Stannanes 3124 6.6. Using the Hurtley Reaction 3124 6.7. Using a Methylenation Reaction 3125 7. Conclusions and Future Prospects 3125 8. Uncommon Abbreviations 3125 9. Acknowledgments 3125 10. Note Added in Proof 3125 11. References 3126 * Authorstowhomcorrespondenceshouldbeaddressed(evano@chimie.uvsq.fr, nicolas.blanchard@uha.fr). † Université de Versailles Saint Quentin en Yvelines. ‡ Université de Haute-Alsace. Chem. Rev. 2008, 108, 3054–3131 3054

Copper-mediated coupling reactions and their applications in natural products and designed biomolecules synthesis.

Microwave irradiation has been successfully applied in organic chemistry. Spectacular accelerations, higher yields under milder reaction conditions and higher product purities have all been reported. Indeed, a number of authors have described success in reactions that do not occur by conventional heating and even modifications of selectivity (chemo-, regio- and stereoselectivity). The effect of microwave irradiation in organic synthesis is a combination of thermal effects, arising from the heating rate, superheating or “hot spots” and the selective absorption of radiation by polar substances. Such phenomena are not usually accessible by classical heating and the existence of non-thermal effects of highly polarizing radiation—the “specific microwave effect”—is still a controversial topic. An overview of the thermal effects and the current state of non-thermal microwave effects is presented in this critical review along with a view on how these phenomena can be effectively used in organic synthesis.

Microwaves in organic synthesis. thermal and non-thermal microwave effects

Microwave assisted synthesis – a critical technology overview

The iodothyronine deiodinases initiate or terminate thyroid hormone action and therefore are critical for the biological effects mediated by thyroid hormone. Over the years, research has focused on their role in preserving serum levels of the biologically active molecule T3 during iodine deficiency. More recently, a fascinating new role of these enzymes has been unveiled. The activating deiodinase (D2) and the inactivating deiodinase (D3) can locally increase or decrease thyroid hormone signaling in a tissue- and temporal-specific fashion, independent of changes in thyroid hormone serum concentrations. This mechanism is particularly relevant because deiodinase expression can be modulated by a wide variety of endogenous signaling molecules such as sonic hedgehog, nuclear factor-κB, growth factors, bile acids, hypoxia-inducible factor-1α, as well as a growing number of xenobiotic substances. In light of these findings, it seems clear that deiodinases play a much broader role than once thought, with great ramifications for the control of thyroid hormone signaling during vertebrate development and metamorphosis, as well as injury response, tissue repair, hypothalamic function, and energy homeostasis in adults.

Cellular and Molecular Basis of Deiodinase-Regulated Thyroid Hormone Signaling

Thyroxine (T4) is the predominant form of thyroid hormone (TH). Hyperthyroidism, a condition associated with excess TH, is characterized by increases in metabolic rate, core body temperature and cardiac performance. In target tissues, T4 is enzymatically deiodinated to 3,5,3′-triiodothyronine (T3), a high-affinity ligand for the nuclear TH receptors TRα and TRβ, whose activation controls normal vertebrate development and physiology1. T3-modulated transcription of target genes via activation of TRα and TRβ is a slow process, the effects of which manifest over hours and days. Although rapidly occurring effects of TH have been documented, the molecules that mediate these non-genomic effects remain obscure2,3. Here we report the discovery of 3-iodothyronamine (T1AM), a naturally occurring derivative of TH that in vitro is a potent agonist of the G protein–coupled trace amine receptor TAR1. Administering T1AM in vivo induces profound hypothermia and bradycardia within minutes. T1AM treatment also rapidly reduces cardiac output in an ex vivo working heart preparation. These results suggest the existence of a new signaling pathway, stimulation of which leads to rapid physiological and behavioral consequences that are opposite those associated with excess TH.

3-Iodothyronamine is an endogenous and rapid-acting derivative of thyroid hormone.

Increasing rates of reaction: microwave-assisted organic synthesis for combinatorial chemistry.

Butane 2,3-Bisacetal Protection of Vicinal Diequatorial Diols.

We have previously shown that several thyronamines, decarboxylated and deiodinated metabolites of the thyroid hormone, potently activate an orphan G protein-coupled receptor in vitro (TAAR1) and induced hypothermia in vivo on a rapid time scale [Scanlan, T. S.; Suchland, K. L.; Hart, M. E.; Chiellini, G.; Huang, Y.; Kruzich, P. J.; Frascarelli, S.; Crossley, D. A.; Bunzow, J. R.; Ronca-Testoni, S.; Lin, E. T.; Hatton, D.; Zucchi, R.; Grandy, D. K. 3-Iodothyronamine is an endogenous and rapid-acting derivative of thyroid hormone. Nat. Med. 2004, 10 (6), 638−642]. Herein, we report the synthesis of these thyronamines. Additionally, a large number of thyroamine derivatives were synthesized in an effort to understand the molecular basis of TAAR1 activation and hypothermia induction. Several derivatives were found to potently activate both rTAAR1 and mTAAR1 in vitro (compounds 77, 85, 91, and 92). When administered to mice at a 50 mg/kg dose, these derivatives all induced significant hypothermia within 60 min ...

Matthew E. Hart

Papers

3-Iodothyronamine is an endogenous and rapid-acting derivative of thyroid hormone.

Increasing rates of reaction: microwave-assisted organic synthesis for combinatorial chemistry.

Butane 2,3-Bisacetal Protection of Vicinal Diequatorial Diols.

Trace amine-associated receptor agonists: synthesis and evaluation of thyronamines and related analogues.

Modified norcantharidins; synthesis, protein phosphatases 1 and 2A inhibition, and anticancer activity.