Pyrolysis of spirotrithianes

Fraser, P. S.; Robbins, Larry V.; Chilton, William Scott

doi:10.1021/jo00931a009

Cited by 18 publications

(3 citation statements)

References 7 publications

(7 reference statements)

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“…Thus the experimental and calculational results strongly indicate that l a (like lb, which yields benzocyclobutenone (3)) gives benzocyclobutenthione, a compound that has not been described in the chemical literature as far as we are aware. Because thiones that lack bulky substituents a to C=S trimerize readily (15), benzocyclobutenthione undoubtedly is a transient species. Our work suggests that the vacuum pyrolysis of l a and its substituted analogues may provide a useful general route to 6a and substituted benzocyclobutenthiones.…”

Section: Methodsmentioning

confidence: 99%

A study of the vacuum pyrolysis of 4-diazoisothiochroman-3-one with Hel ultraviolet photoelectron spectroscopy

Ma¹,

Roy²,

Kresge³

et al. 1996

Can. J. Chem.

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A newly developed ultraviolet photoelectron spectrometer apparatus that utilizes a tunable 50 W CW CO:, laser as a directed heat source is used to study the vacuum pyrolysis of 4-diazoisothiochroman-3-one (la). Analysis of the pyrolysate with ultraviolet photoelectron spectroscopy shows that l a undergoes a facile pyrolysis at a laser power level of less than 26 W, yielding two new compounds: thiaketene 3a, the product of a Wolff rearrangement, and benzocyclobutenthione (6a), which can be derived from thiacarbene 4a, the decarbonylation product of 3a. Activation enthalpieslenergies calculated at the AM 1 and ab initio levels of theory indicate that, unlike the case of 4-diazoisochroman-3-one (lb), the Wolff rearrangement of the incipient carbene may be concerted with loss of nitrogen from l a . The activation enthalpylenergy calculated for the decarbonylation of 3a is significantly higher (AM1,20.5 kcallmol; RHFl6-3 lG(d), 11.7 kcallmol; MP2(full)llRHFl6-31G(d), 14.3 kcallmol) than the activation enthalpylenergy for the decarbonylation of 3b. This result is in keeping with the fact that we detect 3a, but 3b is not found in detectable amounts in the pyrolysate of lb.Key words: vacuum pyrolysis, 4-diazoisothiochroman-3-one, He1 ultraviolet photoelectron spectroscopy, AM1 and ab initio calculations.Resume : On a utilist un spectromktre de photoCmission de photoklectrons dans l'ultraviolet rkcemment mis au point qui utilise un laser ajustable au CO1 de 50 W CW comme source dirigCe de chaleur, pour Ctudier la pyrolyse sous vide de la 4-diazoisothiochroman-3-one (la). L'analyse du pyrolysat par la spectroscopie de photoCmission de photoClectrons dans l'ultraviolet montre que le composC l a subit facilement la pyrolyse i un niveau de puissance du laser infkrieure i 26 W pour donner deux nouveaux composCs : la thiacCt2ne 3a, le produit d'un rearrangement de Wolff, et la benzocyclobutenthione (6a) qui peut provenir du thiacarbkne 4a, le produit de dCcarbonylation du produit 3a. Les Cnergieslenthalpies d'activation calculCes aux niveaux thkoriques AM1 et ab initio indiquent que, contrairement au cas de la 4-diazoisochroman-3-one (lb), la transposition de Wolff du carbkne naissant peut-&tre concertCe avec la perte d'azote i partir de la. L'tnergielenthalpie d'activation calculte pour la dCcarbonylation de 3a est de f a~o n significative plus ClevCe (AM1,20,5 kcallmol; RHFl6-31G(d), 11,7 kcallmol; MP2(complet)llRHFl6-3 lG(d), 14,3 kcallmol) que 1'Cnergielenthalpie d'activation pour la dkcarbonylation de 3b. Ce rCsultat est en accord avec le fait que nous avons detect6 le composC 3a mais le compost 3b n'est pas present en quantitks detectables dans le pyrolysat de lb.Mots clPs : pyrolyse sous vide, 4-diazoisothiochroman-3-one, He1 spectroscopie de photoCmission de photoClectrons dans l'ultraviolet, calculs AM1 et ab initio.[Traduit par la rkdaction] I

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Section: Methodsmentioning

confidence: 99%

A study of the vacuum pyrolysis of 4-diazoisothiochroman-3-one with Hel ultraviolet photoelectron spectroscopy

Ma¹,

Roy²,

Kresge³

et al. 1996

Can. J. Chem.

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“…Indeed, even simple thiocarbonyl compounds 2 exist in equilbria (eq 1) with appreciable amount of the thioenol . For example, the low-pressure pyrolysis of spirotrithienes 3 gives mixtures of cyclic thioketones ( 4 ) and their tautomeric cyclic thioenols 5 (eq 2). For five- and seven-membered rings the percentage of 5 was ca.…”

Section: Introductionmentioning

confidence: 99%

Triphenylethenethiol. Structure, Equilibria with the Thioketone, Solvation, and Association with DMSO

Selzer

Rappoport

1996

J. Org. Chem.

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The simple thioenols, triphenylethenethiol (12) and 2,2-diphenyl-1-anisylethenethiol (13) were prepared. Both are the only observed constituent of the thioenol ⇌ thioketone equilibria and comparison and estimation suggested that the thiocarbonyl ⇌ thioenol equilibrium constant K enol for 12 and other simple thioenols is ≥106 higher than for the corresponding carbonyl ⇌ enol equilibria. The X-ray diffraction of 12, which is the first measured for a simple thioenol, shows a propeller arrangment of the three rings. The δ(SH) in the 1H NMR spectrum increases with the increase in the hydrogen bonding accepting parameter β of the solvent. The association constant K assoc of 12 with DMSO is 0.087, much lower than values of triarylethenols with DMSO. Reaction of diphenylacetaldehyde with Lawesson's reagent did not give the thioenol, but gave bis(2,2-diphenylvinyl) sulfide (16) and a substance (17) having a trithiaphosphorinane system.

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“…We chose to study P because there is a substantial difference in exchange rates of the diastereotopic protons and the substrate does not undergo trin~er-ization, a reaction which unhindered thiones undergo very readily (4).…”

Section: Nick H E~r Ymentioning

confidence: 99%

Base-catalyzed hydrogen isotope exchange of thiocamphor: α-thioenolization rate constants

Andrews¹

1978

Can. J. Chem.

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The rates of base-catalyzed protium-deuterium exchange (a-thioenolization) of the exo and endo protons of thiocamphor (I), in 2: 1 dioxane-D,O at 25.0 i 0.5"C, have been determined by monitoring the uptake of deuterium mass spectrometrically. The exo and erzdo exchange rate constants, 2.20 x lo-' and 5.60 x M -I s-I , respectively, are 23.2 and 12.3 times larger than the rate constants for exo and erzdo exchange in camphor (2). Factors which may determine the rate enhancements are discussed. NICK H E~R YWERSTIUK et PAUL ANDREWS. Can. J. Chem. 56, 2605Chem. 56, (1978. Faisant appel a la spectrornetrie de masse pour evaluer l'absorbtion du deuterium, on a determine les vitesses, catalysees par les bases, des Cchanges protium-deuterium (a-thioeno- Thione-thioenol tautomeris~n was first studied by Reyes and Silverstein in 1958 (1). Since then other workers have attempted to detail the factors which afTect the equilibrium (2, 3). However, u p to the present time, there have been no reports ; f studies of acid-or base-catalyzed a-thioenolization of thiones. In this communication, we report the rates of base-catalyzed protiurn-deuterium exchange of the exo and endo protons in thiocamphor (I) and discuss possible rate-co~ltrolling factors.We chose to study P because there is a substantial difference in exchange rates of the diastereotopic protons and the substrate does not undergo trin~er-ization, a reaction which unhindered thiones undergo very readily (4).The rate constants listed in Table 1 were obtained by the method developed in these laboratories (5). That good first-order kinetics were observed and that analytical gas chromatographic analysis showed no significant conversion of I into 2 established that sulfur-oxygen exchange, a potentially complicating process that \vould decrease the base concentration, is insignificant.Several factors may contribute to the increase in the a-deprotonationl rates of 1 relative to 2. Because 'We have established through several exploratory runs that [3-thioenolization (hon~othioenolization) of 3,3,6,6-tetramethylbicyclo[2.2.1]heptan-2,5-dithione occurs more readily than a-enolization (homoenolization) of 3,3,6,6-tetramethylbicyclo[2.2.1]heptan-2,5-dione (7). oxygen is more electronegative than sulfur and the carbonyl group would be expected to be more electron withdrawing than the thiocarbonyl group, base-catalyzed hydrogen isotope exchange of ketones should be more facile than exchange of thiones. From a survey of carbonyl and thiocarbonyl compounds (8), it is clear that the dipole moments of the thiocarbonyl compounds are close to or greater than the dipole moments of the carbonyl compounds. The

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Pyrolysis of spirotrithianes

Cited by 18 publications

References 7 publications

A study of the vacuum pyrolysis of 4-diazoisothiochroman-3-one with Hel ultraviolet photoelectron spectroscopy

A study of the vacuum pyrolysis of 4-diazoisothiochroman-3-one with Hel ultraviolet photoelectron spectroscopy

Triphenylethenethiol. Structure, Equilibria with the Thioketone, Solvation, and Association with DMSO

Base-catalyzed hydrogen isotope exchange of thiocamphor: α-thioenolization rate constants

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