Of thiopyrans, selenopyrans, and

The third chapter is by J. Kuthan, P. Sebek, and S. Bohm of the Institute of Chemical Technology (Prague, The Czech Republic). It discusses developments in the chemistry of thiopyrans, selenopyrans, and teluropy-rans since 1983 and thus updates Kuthan s own chapter in Volume 34 of Advances, published in 1983. 

Kuthan, J., Sebek, P., Bohm, S., Developments to the Chemistry of Thiopyrans, Selenopyrans, and Telluropyrans, 59, 179. 

Dehydroacetic acid, triacetic acid lactone, and related pyrones, 53, 1 Developments in the chemistry of furans (1952-1963), 7, 377 of Reissert compounds (1968-1978), 24, 187 of thiopyrans, selenopyrans, and telluropyrans, 59, 179... 

The chemistry of six-membered heterocycles containing one selenium or tellurium atom was initially covered in CHEC-11(1996) (chapter 5.11). This updated chapter primarily deals with material dating from 1993 and is complete to 2005 with occasional references from 2006. The structures and nomenclature of the selenium- and tellurium-containing heterocycles discussed in this chapter are included in Figure 1. One major review of tellurium-containing heterocycles has appeared . The chemistry of thiopyrans, selenopyrans, and telluropyrans has also been reviewed <1994AHC180>. 

Advances in the chemistry of thiopyranes, selenopyranes, and telluropy-ranes 93AHC(59)179. 

Equilibrium aromatizations of 4//-pyran (5), 4//-thiopyran (7), and 4H-selenopyran (8) with appropriate pyrylium ions were explored for the estimation of relative stabilities of the latter.351... 

A number of examples of the typical thiopyran transformations to corresponding thiopyrylium ions and dihydro or tetrahydro derivatives have been described in the last decade. Similar behavior was found with a selenopyran. 

Two examples involving as key intermediates the corresponding thio- or selenopyran anions are mentioned in Section IV,A,2, e.g., 48e — 60 + 56 (R = /-Bu) and 54d + 55d -> 59 (85CL1119 90ACS524). A deuteriode-protonation of 2,6-diphenyl-2//-thiopyran (87) to 4-deuterio-2,6-diphenyl-4//-thiopyran (51) took place after the initial reaction with BuLi-THF at... 

Ultraviolet spectra of heteropyrans have been used mainly for characterization purposes. No theoretical calculations of the spectral patterns have yet been done. Typical UV absorption characteristics of some thiopyrans and teluropyrans are collected in Table IX. Analogous insight into the UV absorption of selenopyrans is still lacking. 

Pyrans, thiopyrans, and selenopyrans are comprehensively reviewed by Kuthan in the first unified treatment of this subject. The triazolopyridines were last reviewed in 1961 the chemistry of these five heterocyclic systems is covered by Jones and Sliskovic. 

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