Sulfur-containing heterocycle synthesis

Thus, the reaction of 4-dialkylaminobut-3-yn-2-ones with various bifunctional reagents makes it possible to carry out a targeted synthesis of five- and six-membered nitrogen-, oxygen-, and sulfur-containing heterocycles having two heteroatoms. 

The various possibilities for the first two types of syntheses are listed schematically in Table 4, and the possibilities for synthesis from other heterocycles are listed in Table 5. In each case the method is discussed in more detail in the following sections Tables 4 and 5 indicate the section(s) in which a particular reaction is described. In the case of sulfur-containing heterocycles, 5-oxides and 5,5-dioxides are treated alongside the basic parent structures, since for 1,3,2-dioxathiolane, 1,2,3-oxadithiolane, and 1,2,5-oxadithiolane the unoxidized rings are unknown. 

In comparison with other 1,3-dipoles that have been extensively explored in organic synthesis (7), sulfur-centered 1,3-dipoles (1-4) are rather uncommon species. However, within the last two decades, remarkable progress has been made regarding both methods of generation and synthetic applications. In particular, thiocarbonyl ylides (1) were established as key intermediates useful for the preparation of sulfur-containing heterocyclic compounds. General methods for the preparation of thiocarbonyl ylides and their chemical reactivity have been reviewed (8-11). 

Thio-Claisen Rearrangement in the Synthesis of Sulfur-containing Heterocyclic Compounds A. V. Anisimov and E. A. Viktorova, Khim. Geterotsikl. Soedin., 1980, 435-449. 

Preparation and Use of Nitrogen- or Sulfur-containing Heterocycles in Organic Synthesis ... 

There is a rich synthetic potential for enamines in heterocyclic synthesis. Enamines can react as electrophiles or nucleophiles and as new partners in cycloaddition reactions. Various derivatives of nitrogen-, oxygen-, and sulfur-containing heterocycles have been prepared, and these, in turn, are of interest as starting materials for additional syntheses. They represent potential synthons for the development of various new directions in organic chemistry. 

Electrophilic sulfur species such as thionyl chloride are frequently used in the synthesis of sulfur-containing heterocycles and, for example, reaction with N-N 1,5-dinucleophiles is a direct route to 1,2,6-thiadiazine 1-oxides. Thus the thiadiazines (138 n-1) are readily prepared by treatment of (231) with thionyl chloride in pyridine (81JCS(Pl)l89l), and the benzothiadiazine (232) is similarly made from (233) (64JOC2717). Reaction of (234) with thionyl chloride gives the dithiatriazine (235) (74ZOR488). 

There is a wealth of NMR data available on sulfur-containing heterocyclic systems. There are however, still relatively few papers dedicated to discussion of their NMR spectra. The majority of the spectroscopic data discussed in this work has been selected from papers concerned with either the synthesis or reactivity of the six-membered sulfur heterocycles. Chemical shifts are reported in ppm for spectra recorded in CDCI3 solution unless otherwise stated. Early NMR spectroscopic data have featured in the previous editions of Comprehensive Heterocyclic Chemistry and NMR Spectra of Simple Heterocycles by Batterham is still of fundamental importance for rapid access to H NMR data on the parent sulfur heterocycles . 

Shvartsberg MS, Ivanchikova ID (2003) Synthesis of sulfur-containing heterocyclic compounds by cyclocondensation of acetylenic derivatives of anthraquinone with sodium sulfide. ARKIVOC 13 87-100... 

The application of ionic hydrogenation to sulfur-containing heterocycles is of special significance as heterogeneous catalysts are usually poisoned by sulfur compounds. This fact makes tetrahydrothiophenes, in particular, rather difficult to prepare. Thus, ionic hydrogenation is an extremely powerful and efficient method for the preparation of this class of compounds21,24, as illustrated in the synthesis of biotin derivatives 225. 

Kita Y, Egi M, Okajima A, Ohtsubo M, Takada T, Tohma H (1996) Hypervalent iodine(lll) induced intramolecular cyclization of substituted phenol ethers bearing an alkyl azido side-chain - a novel synthesis of quinone imine ketals. Chem Commun 1491-1492 Kita Y, Egi M, Ohtsubo M, Saiki T, Takada T, Tohma H (1996) Novel and efficient synthesis of sulfur-containing heterocycles using a hypervalent iodine(lll) reagent. Chem Commun 2225-2226... 

Besides the extensive applications of the Lawesson s reagent as already mentioned, this reagent has been used to synthesize many five- and six-membered phosphoms heterocycles, and sulfur-containing heterocycles in addition, this compound has also been used as the racemization-free coupling reagent in peptide synthesis, and the 1,3-dipole indicator. ... 

Heterocycle Synthesis. Methyl thioglycolate is a very interesting building block because the thiol function and the active methylene group are both potential nucleophiles and the ester group is an electrophile. Like other polyfunctional molecules, every functional group may react individually or in combination with the others. This ability has been widely used for the synthesis of sulfur containing heterocycles as exemplified in eqs and 2. ... 

Scheme 4.30 Pd-catafyzed synthesis of sulfur-containing heterocycles.

Two more syntheses of CJH are presented here. The first synthesis relies on setting olefin stereochemistry by incorporating it into a ring (recall the first Corey synthesis of CJH shown on CJH-9). The idea was to use a sulfur-containing heterocycle to establish double bond geometry and then reduce the two carbon-sulfur bonds to liberate the acyclic olefin. Thus, it was hoped that 142 would serve as a precursor of 1 that could be stitched together from 143-145. 

Sulfur-containing heterocycles have rarely been used in ROP even though they are interesting for a variety of biomedical applications. Heterocycles higher than four membered cannot be polymerized by an anionic mechanism. While the cationic polymerization of thietanes leads to branched polymers or crosslinked networks, higher sulfur heterocycles were never used in the synthesis of hyperbranched polymers by ROP, since the synthesis of linear polymers is already... 

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