Hantzsch chemistry

ARTHUR RUDOLF HANTZSCH great chemist and teacher and pioneer of thiazole chemistry... 

For single rings (i.e. mononuclear systems) up to ten atoms in size, there is no question but that Hantzsch-Widman names are overwhelmingly the most widely used, and specialists can be presumed to recognize them readily. However, when one of the trivial names of Table 1 can be used, it prevails almost exclusively. Thiophene will be immediately understood by specialists and most nonspecialists, whereas thiole will distract the reader s attention from the chemistry while he considers the writer s intention is the Hantzsch-Widman system indeed being used, or is it a typographical error Chemical Abstracts also uses these trivial names in its indexes. 

Combinatorial approaches have been applied to this chemistry. In a method amenable to split and pool, PAL, or Rink resin, 89 is modified with an acetoacetate to generate the solid supported aminocrotonate 90. Either a two- or three-component Hantzsch protocol is followed to produce 91. Treatment with TFA carries out the cleavage from the resin and the cyclization to dihydropyridine 92. 

Microwave chemistry has been found to be a useful method for accelerating reactions or catalyzing reactions that are difficult to carry out by other methods. A modification of the Hantzsch method to directly obtain pyridines has been communicated. A dry medium using ammonium nitrate bentonitic clay system with microwave irradiation affords pyridines 96 in a single pot within 5 minutes. When the pyridine is not the major product (> 75% yield), the dealkylated pyridine 97 becomes an... 

The known but newer, more elaborate approach to 4//-thiopyrans by procedures A, B, and C (Scheme 1) resembles the Hantzsch-like syntheses of 4iT-pyrans (83AHC145, Section III,D). The results are summarized in Table I for 3,5-dicyano products 21. The chemistry of cyanothioacetamide as the key starting component has also been reviewed (86H2023 87H205). Cyclocondensations A to C usually proceed under mild conditions and afford 21 in satisfactory yields. 

Blomstrand s formula, which had been largely disregarded, was rediscovered practically simultaneously by Bamberger (1895a) and Hantzsch (1895), who recognized how well it meets the experimental facts. Hantzsch, one of the precursors of physical organic chemistry, also realized the cationic character of these compounds and proposed the present name diazonium ion. 

Bamberger s arguments were based mainly on classical organic chemistry, e.g., formation of derivatives, whereas Hantzsch was already using physicochemical methods. It took Bamberger 18 years to abandon his negative attitude towards the diazoate stereoisomerism (Bamberger and Baudisch, 1912). 

A widely significant and crucial investigation of the mechanism of diazotization was made in 1899 by Hantzsch and Schumann widely significant because it was one of the first mechanistic investigations using appropriate methods of organic chemistry - extremely crucial because it influenced all subsequent investigations in the field of diazotization mechanisms until 1958. 

All the same, lasting credit is due to Hantzsch for refuting the proposals, made so often since 1894, to interpret the isomerism of diazo derivatives using other than stereochemical arguments. For his purpose Hantzsch used the methods of physical chemistry, such as conductivity measurements and spectroscopy, at a time when these were most unusual in the organic field. 

IUPAC Commission on Nomenclature of Organic Chemistry, Revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles, Pure Appl. Chem., 55, 409-416 (1983). 

In 1922, Helferich married Hildegard Kohlrautz. Five children were bom of this very happy and harmonious marriage. In the spring of 1925, Helferich accepted the offer of the Chair in Chemistry and the Directorship of the Chemical Institute at the University of Greifswald, becoming the successor to Pummerer. In the summer semester of 1930, he accepted the offer of the Chairmanship of the Chemical Institute at Leipzig as the successor to Hantzsch. 

A survey of microwave activation in the chemistry of Hantzsch 1,4-dihydropyridines (1,4-DHP) has recently been reported [98]. The experimental method proposed more than a century ago remains the most widely used to synthesize these heterocycles. Since 1992 this process has been adapted to microwave irradiation under a variety of conditions to reduce the reaction time and enhance the yield. Among these experiments, Zhang [99] reported a solvent-free process starting from 3-aminocrotonate... 

Arthur Hantzsch at Wurzburg had difficulty getting his papers published because organic chemists editing the Berichte of the German Chemical Society insisted on the use of classical chemical methods for establishing the identity of a compound rather than methods of cryoscopy or spectroscopy. See Jeffrey Johnson, "Hierarchy and Creativity in Chemistry, 18711914," Osiris, 2d ser., 5 (1989) 214240, on 234. 

He was sent by the Japanese Government to Europe in 1910. He first stayed in the laboratory of A. Hantzsch in Leipzig, and soon moved to the laboratory of A. Werner (1866-1919) in Zurich to leam Coordination Chemistry. He also stayed in the laboratory of G. Urban of the University of Paris to study spectroscopy. He returned from Europe in 1913 with a spectrometer made by Adam Hilger Co. in England, which is the first equipment to be able to measure spectra of solution in Japan, and he used the equipment for the measurements of spectra of coordination... 

In the early Gatterman s preparative chemistry book, " the one-pot synthesis of dUiydropyridine derivatives like those formed by the Hantzsch reaction was one of practical laboratory exercises. 

The photolysis or thermolysis of diazo compounds results in the formation of carbenes. These reactions were identified as early as 1901 by Hantzsch and Lehmann D and Staudinger and Kupfer who decomposed diazomethane photochemically and thermally, respectively. The subsequent work of Hine 3) and Doering ) started the era of carbene chemistry. Excellent reviews of the chemistry of carbenes are available 5-27),... 

Galatsis, P. Hantzsch Dihydro-Pyridine Synthesis In Name Reactions in Heterocyclic Chemistry, Li, J. J. Corey, E. J., Eds. Wiley Sons Hoboken, NJ, 2005, 304—307. (Review). 

The normal Hantzsch synthesis leads to a symmetrical product. The diesters formed may be hydrolysed and decarboxylated using base to give pyridines with less substitution. Note that we are using the ester groups as activating species to facilitate enolate anion chemistry (see Section 10.9)... 

Keywords 1,3-Dicarbonyls, Biginelh reaction, Hantzsch reaction, Heterocyclic chemistry, Knoevenagel condensation, Mannich reaction, Michael addition, Multi-component reactions... 

The modified element name sila indicates replacement in the carbon skeleton, and similar treatment can be applied to other element names. The parent hydride names of Table 5.2 may all be adapted in this way and used in the same fashion as in the oxa-aza nomenclature of organic chemistry. In inorganic chemistry, a major use is in names of cyclic derivatives that have heteroelement atoms replacing carbon atoms in structures. It may be possible to name such species by Hantzsch-Widman procedures (see p. 77), and these should always be used when applicable. 

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