The First Synthesis and Properties of 2,3-Di-t-butylthiophene. Reaction of 3,4-Di-t-butyl-1,2-dithiete with Dimethyl Acetylenedicarboxylate

Abstract

Heating 3,4-di-t-butyl-1,2-dithiete (5) with dimethyl acetylenedicarboxylate (5 equiv) in refluxing o-dichlorobenzene affords dimethyl 2,5-di-t-butyl-3,4-thiophenedicarboxylate (6) (44%), dimethyl 2,3-di-t-butyl-4,5-thiophenedicarboxylate (7) (5%), tetramethyl 1,4-dithiin-2,3,5,6-tetracarboxylate (8) (4%), and tetramethyl 2,3,4,5-thiophenetetracarboxylate (9) (43%). Mechanism of the formation of these products is discussed. Treatment of the hindered ester 7 with lithium 1-propanethiolate affords 2,3-di-t-butyl-4,5-thiophenedicarboxylic acid (13) in 59% yield, which can be decarboxylated by treatment with copper powder to give 2,3-di-t-butylthiophene (4) in 88% yield. The thiophene 4 rearranges to 2,4-di-t-butylthiophene (1) on treatment with aluminum chloride. Oxidation with m-CPBA affords the corresponding sulfone (23). Electrophilic substitutions (bromination and nitration) of 4 occur exclusively at the less hindered and more electronically favored 5-position.

Unique effects of sulfur and water on the syntheses of thiaheterocycles

“…This inference is consistent with the fact that compounds containing carboncarbon single bonds are only generated with the existence of water. Along with the desulfurization from 4, 6 is derived as demonstrated by Nakayama and coworkers [6,[34][35][36]. As for 9 and 10, we extrapolate that sulfide radical anion (S •− /NaS • ) [37,38] may be liberated by the dissociation of sodium disulfide in the system.…”

“…1 H and 13 C NMR spectra were recorded on a Bruker Avance 400 spectrometer or on a Bruker Avance 600 spectrometer (Bruker Corporation, Bruker AXS Inc., Madison, WI) in CDCl 3 or in acetone-d 6 . High-resolution mass spectra were recorded on a Thermo Scientific LTQ/FT mass spectrometer (Thermo Scientific, West Palm Beach, FL) or on a GCT mass spectrometer.…”

“…Therefore, heterocyclic vinyl thioethers motivated great interest among organic chemists to know more about them. After the isolation of 3,4-bis(trifluoromethyl)-1,2-dithiete [3], the reactions of 1,2-dithiete derivatives [4][5][6] and their isomers [7,8] with other compounds, such as alkenes [8], alkynes [6,8,9], and oxidants [7], have been extensively studied. On the contrary, halogenated alkenes or alkynes treated with inorganic sulfides also produced desirable thiaheterocyclic compounds [10][11][12][13].…”

Polyimides Containing 1, 4-Dithiine Units and their Corresponding Thiophene 2, 3, 4, 5 Tetracarboxylimide Units

“…When the compound 5 was heated to melting point (∼240 • C), 1 atom of sulfur was expelled exothermically and sublimed from the melt giving thiophene derivate 6, in nearly quantitative yield. Thermal sulfur extension of 1,4-dithiines yielding thiophenes is well documented [18][19][20][21]. All model compounds had characteristic absorptions for maleimide in the region 1720, 1385, 1140 and 740 cm −1 .…”

Photochemistry of Tetraalkyl‐2H‐thietes

“…-Except for 2,3-di(tert-butyl)thiophene, which has been obtained in very low yield in a multistep synthesis starting from 3,4-di(tert-butyl)-l,2-dithiete [7], 2,3-dialkylthiophenes with t-Bu group at C(2) have not been reported [8]. Whereas treating 3-methyl-4-oxopentanoic acid with P,S, at 130" gave 2,3-dimethylthiophene in only 3 % isolated yield [9], similar treatment of esters 4 in tetralin at 160" affords thiophenes 5 in reasonable yield (36-53 YO).…”