N-(Hydroxy)thiazole-2(3H)-thiones 6-10 have been prepared atom). (iii) Based on the results of X-ray diffraction studies and on the 1 H-and 13 C-NMR spectra, guidelines for the in a short and efficient synthesis from p-substituted acetophenones. Alkylation of heterocycles 6-10 in the form characterization of N-(alkoxy)thiazolethiones 16-20 and 2-(alkylsulfanyl)thiazole N-oxides 21-25, i.e. the products of S-of their potassium or tetraalkylammonium salts 11-15 affords N-alkoxy-4-arylthiazole-2(3H)-thiones 16-20 in good to alkylation of thiohydroxamate salts 11-15, could be derived.
(iv) Photolyses of substituted N-(4-pentenoxy)-4-satisfactory yields. The hitherto unknown thiones 16-20 have been subjected to a detailed structural investigation (NMR arylthiazolethiones 16-20 in general and in particular of pchloro derivatives 19 were carried out in the presence of the spectroscopy and X-ray crystallography) and furthermore to a mechanistic study in order to explore their utility as sources hydrogen donor Bu 3 SnH, and afforded substituted tetrahydrofurans 31 or tetrahydropyrans 32 as major products of oxygen-centered radicals in solution. From the results of these studies, the following conclusions can be drawn: (i) X-in good yields. The observed stereo-and regioselectivities of ethers 31 and 32 point to alkoxyl radicals 30 as reactive ray analyses of the p-chlorophenyl-substituted acid 9, of the O-alkyl derivatives 19c, 19f, and of the O-mixed anhydride intermediates, which add intramolecularly by selective 5exo-trig or 6-endo-trig pathways to the olefinic double
and long N-O connectivities [N3-O1 = 1.369(3)-1.379(2) A ˚] bonds. In terms of synthetic access and ease of handling of the radical precursors, the p-chlorophenyl-substituted in the thiohydroxamate functionalities. Furthermore, Oalkyl-or O-acyl substituents at O1 are twisted out of the thiazolethiones 9 and 19 exhibit significant advantages over all the other thiones used in this study and are considered thiazolethione plane by ca. 90°, which points to lone-pair repulsion between nitrogen and oxygen atom as the as excellent substitutes for the pyridinethiones as efficient sources of free alkoxyl radicals. Consequently, the present underlying structural motif of the cyclic thiohydroxamate derivatives. (ii) Alkylation of ambidentate thiohydroxamate compounds may be of use in both mechanistic and synthetic studies. anions (salts 11-15; oxygen and sulfur nucleophiles) affords almost exclusively O-esters 16-20 (alkylation at the oxygen carbonϪhydrogen bonds, [10] as well as for ring expansions