Pyrolysis of alkyl sulfide tosylhydrazone salts. Search for R2S-4 participation in carbene reactions. Pyrolysis of sodium toluenesulfinate

Johnson, Peter Y.; Koza, Edward; Kohrman, Robert E.

doi:10.1021/jo00957a010

Cited by 13 publications

(5 citation statements)

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“…Not surprisingly, these isomers give very similar EI mass spectra. 70,71 Its GC retention time fell between those of thiophene and thiophane, consistent with the proposed structure. Peak 3 was assigned to thiophane (10) based in part on its GC retention time.…”

Section: ■ Results and Discussionsupporting

confidence: 81%

“…Peak 2 matched 2,5-dihydrothiophene in the NIST database (74% probability), though it could also be 2,3-dihydrothiophene. Not surprisingly, these isomers give very similar EI mass spectra. , Its GC retention time fell between those of thiophene and thiophane, consistent with the proposed structure. Peak 3 was assigned to thiophane ( 10 ) based in part on its GC retention time.…”

Section: Resultssupporting

confidence: 76%

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Solution Phase Photolysis of 1,2-Dithiane Alone and with Single-Walled Carbon Nanotubes

et al. 2012

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Photolysis of 1,2-dithiane (1) in acetonitrile with single walled carbon nanotubes (SWCNTs) was earlier reported to form thiol-functionalized SWCNTs via the butane-1,4-dithiyl diradical (2). The present study shows that 2 instead undergoes a facile rearrangement to thiophane-2-thiol (6). This photoreaction is clean, rapid, and irreversible under 313 nm irradiation. The secondary photolysis of 6 with SWCNTs at a shorter wavelength (254 nm) leads to 2-thiophanyl radicals 8, which derivatize SWCNTs by covalent attachment. Pyrolysis of the resulting "sulfurized SWCNTs" affords a mixture of organosulfur compounds, including thiophene formed by dehydrogenation. An unknown additional mechanism causes high TGA weight loss and a large incorporation of sulfur.

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Section: ■ Results and Discussionsupporting

confidence: 81%

Section: Resultssupporting

confidence: 76%

Solution Phase Photolysis of 1,2-Dithiane Alone and with Single-Walled Carbon Nanotubes

et al. 2012

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“…following independent synthesis (see below). Analytical data for the mixture of diastereoisomers were identical to those for the mixture obtained from the reaction of tetrahydrothiophene with TiCl,, m/z 174 (80%; M+*), 141 (12), 127 (25), 114 (13), 113 (42), 99 (14), 87 (loo), 86 (1 l), 85 (19), and 45 (20); GH(CDC1,) 3.30 (1 H, m), 2.85 ( 5 H, complex m), 2.58 (1 H, m), 2.1 5 (4 H, complex m) 1.86 (1 H, m), and 1.60 (2 H, m) (Found: C, 55.4; H, 7.9. C,H,,S, requires C, 55.1; H, 8.1%).…”

Section: Component B Was Distilled To Give 3-(tetrahydro-2-thienyf)-mentioning

confidence: 65%

“…Isomer 1: m/z 174 (89%; M+*), 141 (14), 127 (27), 114 (15), 113 (47), 99 (16), 87 (loo), 85 (20), and 45 (20); GH(CDCl,), 3.32 (1 H, q), 2.92 (1 H, m), 2.83 (4 H, m), 2.60 (1 H, t), 2.15 (4 H, complex m), 1.84 (1 H, m), and 1.58 (2 H, m). Isomer 2: m/z 174 (73%; M"), 141 (ll), 127 (21), 114 (12), 113 (37), 99 (14), 87 (loo), 85 (19), and 45 (19); 6,(CDC13) 3.25 (1 H, td), 2.84 (5 H, complex m), 2.53 (1 H, t), 2.14 (4 H, complex m), 1.86 (1 H, m), 1.62 (2 H, m). The 'H n.m.r.…”

Section: Synthesis Of Diustereoisomers Of 3-(tetrahydro-2-thienyf)tet...mentioning

confidence: 99%

Metal-assisted reactions. Part 18. Reaction of titanium tetrachloride with cyclic sulphides: novel bicyclic disulphur compounds

Delaney¹,

Johnstone²,

Boehm³

et al. 1986

J. Chem. Soc., Perkin Trans. 1

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In marked contrast to the reaction of tetrahydrofuran with Ti CI,, tetrahydrothiophene did not afford ring-opened products. Instead, small quantities of ring-dimers were produced, possibly via initial chlorination and dehydrochlorination to produce 2,3-dihydrothiophene. An improved synthesis of 2,3-di hydrothiophene is reported.Reaction of a wide variety of cyclic ethers with TiCl, has been shown to produce mainly dimeric dichloro compounds or chloro alcohols, depending on the method of work-up.2 For example, tetrahydrofuran readily yields either 1,9-dichloro-5-oxanonane or 9-chloro-5-oxanonan-1-01, together with some simple ring-opened 1,4-dichlorobutane or 4-chlorobutan-1-01. Titanium halides also form stable complexes with cyclic sulphide~.~ Attempted ring-opening and dimerization of tetrahydrothiophene with TiCl, did not give ring-opened dimers but did afford a small quantity of a ring-dimer.Merhod-Te t ra h y d ro t hiop hene was refl uxed with TiCl , fo r several hours after which water was added and the organic product was distilled to yield a small quantity of a dimeric compound, CSH14S2. By 'H n.m.r. spectroscopy and synthesis this dimer of tetrahydrothiophene was shown to be 3-(tetrahydro-2-thieny1)tetrahydrothiophene (1) (Scheme); a possible route to this compound involves the intermediate, 2,3-dihydrothiophene. The latter was synthesized in good yield by pyrolysis of 2-benzoyloxytetrahydrothiophene. By introducing 2,3-dihydrothiophene into a reacting mixture of tetrahydrothiophene and TiCl,, an increased yield of the dimer (1) was obtained, together with a number of other products (2)--(5), some of which were synthesized independently. bicyclic structure (6). Structure (1) for the dimer was shown to be correct by independent synthesis. Refluxing a solution of 2-chlorotetrahydrothiophene in benzene afforded the known dimer of 2,3-dihydrothiophene, uiz. 4-(tetrahydro-2-thienyl)-2,3-dihydrothiophene (7).5 Catalytic reduction of sulphurcontaining compounds is hindered by poisoning effects and so the 2,3-dihydrothiophene dimer (7) was reduced to 3-(tetrahydro-2-thieny1)tetrahydrothiophene (1) by use of a mixture of triethylsilane and trifluoroacetic acid.6 Analytical g.c. showed that the reduced product had been obtained as a mixture (cu. 1 : 1) of two diastereoisomers which could be separated by preparative scale g.c. Similarly, the dimer (1) obtained from the reaction of TiCl, with tetrahydrothiophene was also obtained as a diastereoisomeric mixture (cu. 2: 3). The 'H n.m.r. and mass spectra of both diastereoisomers were very similar.Formation of the dimer (1) probably resulted from a small amount of radical chlorination of tetrahydrothiophene by TiCl, (Scheme) followed by elimination of HCl to give 2,3dihydro-thiophene; further radical reaction could give the product (1) as shown in the Scheme. A radical process is preferred as an explanation because an ionic process would require a hydride ion transfer in order to form the fully reduced species (1); ionic dimerization of 2,3-dihydrothiophene is known t...

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“…There are few reports in which tosylhydrazones of cyclic ketones containing sulfur are thermally decomposed at very high temperatures in presence of base whereas photolytic decomposition has resulted in the formation of olefins in poor yields. [4][5][6] However, in these cases regioselectivity in the formation of olefins observed is moderate to poor.…”

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confidence: 99%

A Facile Regioselective Decomposition of Tosylhydrazones: An Application towards the Synthesis of α-Lipoic Acid

Kale¹,

Pasupathy²

2005

Synlett

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A facile regioselective decomposition of tosylhydrazones using NaOH as a base in refluxing isopropyl alcohol is described. This finding has been successfully applied towards the synthesis of (±)-a-lipoic acid (1).The decomposition of tosylhydrazones to olefins has become a popular tool in organic synthesis for conversion of ketones into olefins. 1 The Shapiro reaction 2 permits the convenient conversion of a ketone into a less substituted olefin almost always exclusively, however, it requires strong bases such as alkyl lithium reagents. The BamfordStevens 3 reaction employs very high temperature for decomposition of tosylhydrazones in the presence of base to give olefins. Both olefins and ketones are fundamental building blocks in synthetic organic chemistry; both may be readily and easily transformed into an array of diverse functionality. There are few reports in which tosylhydrazones of cyclic ketones containing sulfur are thermally decomposed at very high temperatures in presence of base whereas photolytic decomposition has resulted in the formation of olefins in poor yields. 4-6 However, in these cases regioselectivity in the formation of olefins observed is moderate to poor.During our approach towards the synthesis of a-lipoic acid (1), it has been found that tosylhydrazones 2a-e on treatment with NaOH in isopropyl alcohol at reflux temperature resulted in the regioselective decomposition of the tosylhydrazones to furnish more substituted olefins 3a-e along with minor amounts of less substituted olefins 4a-e with the regioselectivity of ca. 9:1 (Scheme 1).The tosylhydrazones 2a-e were prepared starting from methyl thioglycolate as shown in Scheme 2. Methyl thioglycolate 5 on acetonoide protection 7 gave 88% of diester 6, which was then subjected to Dieckmann condensation 8 to give cyclic b-ketoester 7 in 86% yield. A singlet at d = 12.60 ppm in the 1 H NMR spectrum of 7 revealed that it existed in the enolic form. After a few trials, conditions for the C-alkylation of b-ketoester 7 were developed with different alkylating agents RX using K 2 CO 3 as a base in the presence of phase transfer catalyst. 9 The C-alkylated products 8a-e were subjected to decarboxylation using Krapcho's protocol 10 to furnish ketones 9a-e in a wide range of yields. The ketones 9a-e were converted into their corresponding tosylhydrazones 2a-e by treament with tosylhydrazine in methanol at room temperature (Table 1). 11The different tosylhydrazones prepared as above, were treated with NaOH in refluxing isopropyl alcohol and the results are summarized in Table 2. It was observed that the tosylhydrazones were decomposed to olefins with the Scheme 2 Reagents and conditions: a) acetone, BF 3 ·Et 2 O (cat.), 0°C to r.t., 6 h, 88%; b) NaH, THF, 60°C, 3 h, 86%; c) K 2 CO 3 , Bu 4 NHSO 4 , THF, r.t., 5-24 h; d) DMSO, NaCl, H 2 O, 135-140°C, 5-8 h; e) TsNHNH 2 , MeOH, r.t., 2-3 h. Scheme 1 reflux, 2-3 h isopropyl alcohol S S R 4a-e (minor) S S NNHTs R S S R + 2a-e 3a-e (major) NaOH

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Pyrolysis of alkyl sulfide tosylhydrazone salts. Search for R2S-4 participation in carbene reactions. Pyrolysis of sodium toluenesulfinate

Cited by 13 publications

References 1 publication

Solution Phase Photolysis of 1,2-Dithiane Alone and with Single-Walled Carbon Nanotubes

Solution Phase Photolysis of 1,2-Dithiane Alone and with Single-Walled Carbon Nanotubes

Metal-assisted reactions. Part 18. Reaction of titanium tetrachloride with cyclic sulphides: novel bicyclic disulphur compounds

A Facile Regioselective Decomposition of Tosylhydrazones: An Application towards the Synthesis of α-Lipoic Acid

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