Axial:Equatorial Rate Ratios. 1. Eliminations Leading to the Exocyclic Methylene Group

King, J. F.; Coppen, M. J.

doi:10.1139/v71-619

Cited by 16 publications

(11 citation statements)

References 13 publications

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“…In marked contrast to the smooth rearrangement of the axial isomer 16a , the rearrangement of the equatorial amide isomer 16b (Ph 3 P/CCl 4 /TEA) gave a very low yield of the product nitrile 18 , albeit in approximately the same A:E ratio as had resulted from the rearrangement of amide 16a (Scheme ). The difference in reactivity between 16a and 16b is most likely a manifestation of steric acceleration or assistance . Both amides are probably converted to their respective imidoyl halides at a similar rate.…”

Section: Resultsmentioning

confidence: 99%

Rearrangements of Substituted 3-Aza-1,2,5-hexatrienes. 3. The Scope and Versatility of an Extremely Mild 3-Aza-Cope Reaction

1996

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An investigation of the [3,3]-sigmatropic reaction of substituted 3-aza-1,2,5-hexatrienes to give 4-pentenenitriles is presented. This reaction has been found to occur under a wide variety of reactions conditions (10 are reported) starting from readily available N-allylamides. In contrast to other 3-aza-Cope reactions, this process occurs at room temperature, under essentially neutral conditions, allowing for the facile preparation of substituted nitrile products in moderate to excellent yields. The scope and versatility of this reaction are demonstrated by its use on a wide variety of substrates, including nitrogen- and oxygen-substituted amides. The rearrangements of cis- and trans-4-tert-butyl-N-allylcyclohexanecarboxamides 16a and 16b are reported and were found to give a ratio of axial to equatorial (A:E) products consistent with A:E ratios found for other related sigmatropic reactions. The stereochemical requirements for this reaction appear to be similar to other [3,3]-rearrangements even though the transition state for this rearrangement is most likely neither boat nor chairlike.

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Section: Resultsmentioning

confidence: 99%

Rearrangements of Substituted 3-Aza-1,2,5-hexatrienes. 3. The Scope and Versatility of an Extremely Mild 3-Aza-Cope Reaction

1996

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“…X 10 in. silica gel dry column (10% ether in hexane) to yield 1.23 g (87%) of the desired product at Rf = 0.3: ir (CC14) 1739, 1625, 1595; NMR (CC14) 5 6.7-7.9 (11 H, m), 3.80 (3 H, s), 3.60 (3 H, s), 3.3-3.8 (1 H, obscured by the methyl singlets), 3.05 (2 H, br t, / = 8), 2.15 (2 H, m); mass spectrum (m/e, %) 368 (3), 367 (8), 366 (33), 259 (13), 258 (25), 256 (14), 197 (38), 184 (23), 172 (36), 171 (100), 153 (23), 141 (17), 129 (17), 128 (100), 115 (20), 109 (26), 77 (15), 67 (21). Caled for C22H22O3S: 366.1289.…”

Section: Methodsmentioning

confidence: 99%

“…After addition was complete, the dry ice-2-propanol bath was replaced by a dry ice-carbon tetrachloride bath (~-25 °C) (preferred method) or the reaction mixture was allowed to warm to room temperature prior to the dropwise addition of diphenyl disulfide (2.19 g, 10.0 mmol) in 5 ml of THF. After stirring at room temperature for 1 h, the reaction mixture was diluted with 100 ml of ether and worked up as usual to yield a yellow oil which was absorbed on 6 g of silica gel and chromatographed on a 200 g silica gel column (5% ether in hexane) to yield 1.48 g (91%) of a pale yellow oil, Rf 0.35: ir (CC14) 1724; NMR (CC14) mixture of isomers 7.1- 7.6 (5 H, m), 6.0-6.5 (2 H, m), 3.Ó-4.3 (2 H, m), 2.8-3.1 (1 H, m), 2.3-2.8 (3 H, m), 0.8-1.8 (7 H, m); mass spectrum (m/e, %) 200 (2), 280 (4), 288 25), 77 (38), 73 (21). Caled for C17H20O2S: 288.1184.…”

Section: Methodsmentioning

confidence: 99%

“…Found: 308.1783. 9: ir (CC14) 1730; NMR (CC14) 3.75 (3 H, s), 3.05 (1 H, d, J = 9 Hz), 2.08 (3 H, s), 1.0-2.0 (7 H, m), 0.7-1.0 (6 H, m); mass spectrum (m/e, %) 206 (2), 205 (4), 204 (21), 201 (18), 157 (17), 145 (24), 129 (14), 127 (85), 120 (100), 116 (38), 115 (14), 101 (22), 97 (23), 88 (46), 83 (16), 61 (23), 57 (87), 55 (55). Caled for C,oH2o02S: 204.1184.…”

Section: Methodsmentioning

confidence: 99%

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New synthetic reactions. Sulfenylations and dehydrosulfenylations of esters and ketones

Trost¹,

Salzmann²,

Hiroi³

1976

J. Am. Chem. Soc.

504

148

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Quenching the enolates of esters and ketones with dimethyl disulfide or diphenyl disulfide produces the corresponding a-sulfenylated products. The regio-and chemospecificity of these reactions are defined. Oxidation to the sulfoxide followed by thermolysis leads smoothly to the @unsaturated systems. Temperatures for the elimination of the phenyl sulfoxides are normally around 50 O C , whereas those for the methyl sulfoxides are normally around 110 O C . In both cases, the presence of the carbonyl group significantly facilitates the elimination. Dipole-dipole effects account, in part, for this effect and rationalize the regioselectivity observed in cyclic cases. In some cases, the use of sulfenic acid traps, amines or trimethyl phosphite, is required for good yields. The synthesis of two bee pheromones demonstrates the utility of this approach for introduction of unsaturation. Conditions for mono-vs. disulfenylation are discussed. Use of the latter to effect conversion of an active methylene group into a carbonyl group is illustrated.

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“…The work described in the accompanying paper (1) was started in the hope of ultimately using the relative rates of axial us. equatorial epimers in the study of reaction mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Axial:Equatorial Rate Ratios and the Mechanism of Formation of Sulfenes by Dehydrohalogenation of Alkanesulfonyl Chlorides

King¹,

Lee²

1971

Can. J. Chem.

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The method of axial: equatorial rate ratios has been applied to the study of themechanism offormation of sulfenes via the reaction of alkanesulfonyl chlorides with base. The axial trans-2-decalinsulfonyl chloride (6) and the equatorial trans-2-decalinsulfonyl chloride (8) were synthesized. The axial sulfonyl chloride 6 was found to react 71 times faster than the equatorial epimer 8 with triethylamine in the presence of aniline at -25", a reaction which evidently proceeds via the sulfene 7. With water at 50" without added base (a reaction believed to take place by direct attack on the sulfur atom) 8 reacts about 14 times faster than 6. It is concluded that the formation of the sulfene 7 from 6 by the action of triethylamine cannot take place by a mechanism involving a slow SN2 reaction followed by a fast bimolecular elimination, and that the most likely route for 6, and other alkanesulfonyl chlorides as well, is the E2 reaction.La mkthode des rapports de vitesse axia1:Cquatorial a kt6 utilisee pour Btudier le mecanisme de la formation des sulf6nes via la reaction des chlorures d'alkanesulfonyles avec une base. Le chlorure de la trans-2-decalinsulfonyle axiale (6) et le chlorure de la trans-2-dCcalinsulfonyle Cquatoriale (8) ont et6 synthttists. Le chlorure de sulfonyle axial 6 reagit 71 fois plus vite que 1'6pimere equatorial 8 avec la triethylamine en presence d'aniline a -25" (reaction qui se fait via le sulfene 7). Dans I'eau a 50°, sans I'adjonction d'une base, (reaction supposke se faire par une attaque directe sur l'atome de soufre) le compose 8 reagit environ 14 fois plus vite que le compose 6. Ces rksultats prouvent que la formation du sulfene 7 a partir de 6, par I'action de la triethylamine, ne peut se faire par un mecanisme impliquant une reaction SN2 lente suivie d'une elimination bimoleculaire rapide. A partir du compose 6, et d'autres chlorures d'alkanesulfonyle, le mecanisme le plus probable est celui faisant intervenir une reaction E2.

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Axial:Equatorial Rate Ratios. 1. Eliminations Leading to the Exocyclic Methylene Group

Cited by 16 publications

References 13 publications

Rearrangements of Substituted 3-Aza-1,2,5-hexatrienes. 3. The Scope and Versatility of an Extremely Mild 3-Aza-Cope Reaction

Rearrangements of Substituted 3-Aza-1,2,5-hexatrienes. 3. The Scope and Versatility of an Extremely Mild 3-Aza-Cope Reaction

New synthetic reactions. Sulfenylations and dehydrosulfenylations of esters and ketones

Axial:Equatorial Rate Ratios and the Mechanism of Formation of Sulfenes by Dehydrohalogenation of Alkanesulfonyl Chlorides

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