Following up on our previous observation that the rate of formation of a β-alkoxy-substituted α-sulfonyl carbanion depends on the stereochemistry of the alkoxy group, we have found similar behaviour when the β-substituent is R2N, RS, or R3N+. With each substituent, the variation of kN (defined by kN = (kexch)X /(kexch)model) is consistent with an equation of the form log kN = a + b cos2θ, where θ is the H-C-C-X torsion angle. We propose that the a term describes the polar (field plus inductive) effect and the b term the negative hyperconjugative effect of the substituent; we show how the variations in a and b may be readily accommodated within this framework. Some features of the trialkylammonio group previously postulated in the literature are discussed in the light of our results.Key words: negative hyperconjugation, substituent effects, stereoelectronic factors, sulfonyl carbanions, anomeric effect.

Bis(trimethylsilyl)methanesulfonyl and tris(trimethylsilyl)methanesulfonyl chlorides (2c and 2d, respectively), have been prepared for the first time. Reactions of 2d with nucleophiles give products evidently derived from bis(trimethylsilyl)sulfene (1c). Reaction of 2c with piperidine gives the same piperidide as that from 2d, presumably via 1c formed by dehydrochlorination of 2c, whereas water and fluoride ion yield products consistent with their formation via trimethylsilylsulfene (1b) formed from 2c by attack at silicon with loss of the trimethylsilyl and chloro groups. No evidence for any enhanced stability in 1c was found.Key words: sulfonyl chlorides, sulfenes, silylsulfonyl chlorides, silylsulfenes, desilylation.

We report evidence for a strongly geometry-dependent substituent effect. The rate constants for H-D exchange of the or-hydrogens, (k(exch))(OR), in a set of 19 beta -alkoxy sulfones of known, fixed (or strongly preferred) H-C-alpha-C-beta-OR torsion angles have been measured. Those of corresponding model compounds lacking the alkoxy group, (k(exch))(model), were also measured, thereby providing the ratio, k(N) = (k(exch))(OR)/(k(exch))(model); the k(N) values so obtained range over more than 4 orders of magnitude. We show that when due allowance is made for steric and other influences, our observations are consistent with an equation of the form log k(N) = a + b cos(2)theta (where a = 1.70 +/- 0.17 and b = 2.62 +/- 0.20). It is further shown that the observed rate constant ratios are not consistent with a substituent effect consisting only of the inductive effect and the field effect, and that they are fully consonant with the additional presence of a third effect, namely negative hyperconjugation or the generalized anomeric effect, specifically a torsion-angle-dependent donation of the partial negative charge of the incipient carbanion into the sigma*(C-O) orbital. This effect is largest with torsion angles of 0 and 180 degrees and at these torsion angles constitutes the major source of stabilization of the incipient carbanion by the beta -alkoxy group. The present observation of a torsion-angle-dependent substituent effect may be combined with the known adherence of the specific rate of alpha -sulfonyl carbanion formation to the Taft equation, to provide an equation yielding torsion angle-dependent Taft sigma* constants for the alkoxy group: (sigma (theta)*)(OR) = 0.35 + 0.55 cos(2)theta. The idea of torsion angle dependence is usefully applied to the long-standing problem of the mechanisms of base-promoted elimination with 2-tosyloxycyclohexyl p-tolyl sulfones.

Hydrolysis of 2,2,2-trifluoroethanesulfonyl chloride (1) is shown to take place by way of the sulfene (CF(3)CH=SO(2)), formed by (a) an irreversible E1cB process over the pH range 1.8-5 with water acting as the carbanion-forming base in the lower pH range and hydroxide anion at higher pH, and (b) a reversible E1cB reaction in dilute acid.

Alkyl 2,2,2-trifluoroethanesulfonate esters (tresylates), ROSO(2)CH(2)CF(3), react with aqueous base (pH >/= 9) to give the (alkoxysulfonyl)acetic acid, ROSO(2)CH(2)COOH; with the further addition of either a primary or secondary amine or of an alkanethiol, the product is the either the corresponding amide, ROSO(2)CH(2)C(O)NR(1)R(2), or a mixture in which the ketene dithioacetal, ROSO(2)CH=C(SR(1))(2), or the thioorthoester, ROSO(2)CH(2)C(SR(1))(3), may predominate. Kinetic and product studies are consistent with the following: (a) the reaction of tresylates with water is the normal sulfonic ester hydrolysis and (b) reaction with hydroxide is an (E1cB)(rev) process with loss of HF to yield the alkyl 2,2-difluoroethenesulfonate, ROSO(2)CH=CF(2), which rapidly yields the observed products. Benzyl 2,2,2-trifluoroethyl sulfone reacts analogously. The relationship between these observation with small molecules and those of earlier workers with tresyl agarose is discussed.

Evidence is presented that the only significant reaction of 2-methyl-2-propanesulfonyl chloride (1) (a) in water over the pH range 3.5-13.0 or (b) in methanol-chloroform-d is an ionization to the tert-butyl cation (2) and the chlorosulfite anion (ClSO2-), followed by further reactions of these species. The organic products include isobutylene (3), tert-butyl chloride (4a), tert-butyl alcohol (4b), and, at high pH, 2-methyl-2-propanesulfinate anion (6) and small amounts of 2-methyl-2-propanesulfonate anion (5). In the presence of barium chloride the rate of hydrolysis of 1 is constant over the pH range 3.5-12.0.

Cyclopropanesulfonyl chloride (1) has been synthesized and its reactions examined to see if the three-membered ring leads to unusual reactions in either 1 or the corresponding sulfene, cyclopropanethione S,S-dioxide (2). pH-rate profiles, primary kinetic isotope effects (KIE's), and pH-product ratio experiments are in full agreement with mechanisms of hydrolysis of 1 like those of a simple alkanesulfonyl chlorides (J. Am. Chem. Soc. 1992,114,1743-1749), specifically, (a) below pH 7.2 by S(N)2-S reaction with water and (b) above pH 7.3, elimination by hydroxide to form the sulfene (2) which is trapped by (i) water below pH 12.0 and (ii) hydroxide above pH 12.0. The products of the reaction of cyclopropanesulfonyl-1-d chloride (9) with triethylamine and 2-propanol in dichloromethane indicate that most of the reaction goes via 2; the analogous reaction with trimethylamine apparently proceeds by a direct formation of the sulfonylammonium chloride (14) which then yields the alpha-deuterated N,N-dimethyl sulfonamide (12, R = Me). The evident sulfene formation processes in the reaction of triethylamine with ethanesulfonyl, 2-propanesulfonyl, and cyclopropanesulfonyl chlorides show very low primary KIE's (<1.5), pointing to highly product-like transition states. Reaction of 1 with an enamine (1-pyrrolidino-2-methylpropene, 20) in the presence of a base in either water or dichloromethane gave cyclopropanesulfonpyrrolidide (23) and an aldehyde adduct (24), but no four-membered cycloadduct (21).

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Single crystal x-ray structures of five cyclopropylsulfonyl compounds all show similar conformations about the (cyclopropyl carbon)-sulfur bond (as in 3) consistent with cyclopropyl-sulfonyl conjugation.

Kinetic, product analysis, and deuteration experiments are consistent with the following mechanisms of hydrolysis of (trimethylsilyl)methanesulfonyl chloride (1) (in 0.01 M KCl at 1-degrees-C): (a) pH less-than-or-equal-to 10.0, attack of water at silicon to form sulfene (5) which is trapped by water to give methanesulfonate anion (3), (b) pH greater-than-or-equal-to 10.0, attack of hydroxide anion (i) at silicon to yield sulfene (5) and (ii) at an alpha-hydrogen to form (trimethylsilyl)sulfene (4), in each case followed by trapping of the sulfene to give either methanesulfonate (3) or (trimethylsilyl)methanesulfonate (6) salts. Aqueous potassium fluoride catalyzes the hydrolysis of 1 with formation of the methanesulfonate 3, evidently by way of silicophilic attack of fluoride anion on 1 with formation of sulfene (5). Reaction of 1 with an enamine 7 in water (at pH 8 or 9), with or without fluoride, gives two characteristic sulfene-enamine products, (i) the four-membered cycloadduct 8 and (ii) the methylsulfonyl aldehyde 9. The same or related products are also obtained from methanesulfonyl, 2-propanesulfonyl, and phenylmethanesulfonyl chlorides and enamines in water (at pH 9). Hydrolysis of 1 is also catalyzed by aniline or triethylamine evidently giving 5.

We present a way of prescribing the pH for a reaction so as to obtain either (a) maximum yield in competition with hydrolysis or (b) selective reaction at either of two sites in such nucleophile-electrophile reactions as C-alkylation of acidic ketones and the acylation and sulfonylation of amines. First, we derive the following general equation for pH(max), the pH giving the highest yield of the product (P) of the reaction of a nucleophile (Nu) with a hydrolyzable electrophile (E) in water: pH(max) = 1/2[log (k(w)/k(OH)) + pK(w) + pK(a)] (k(w) and k(OH) refer to the water- and hydroxide-promoted hydrolyses of E, K(w) is the autoprotolysis constant of water, and K(a) is the acid dissociation constant of NuH+, the conjugate acid of Nu). pH(max) thus depends on a property of E (namely, k(w)/k(OH)) and a property of Nu (the pK(a) of NuH+), but not on the rate constant for the reaction of E with Nu or the concentration of Nu. We then deduce analogous approximate equations for maximum selectivity for reaction at either of two nucleophilic sites, specifically, equations giving pH(xmax) and pH(ymax), the pH values for the maximum yields of the respective products (P(x) and P(y)) of the reactions of E with the two nucleophiles. We find that (a) pH-yield profiles calculated from the equations concur with observed yields for reactions under pseudo-first-order conditions and (b) preparative experiments at the estimated pH values give good to excellent yields of clean products and high selectivity in both the C-alkylation and Schotten-Baumann reactions.

pH-rate profiles, primary kinetic isotope effects, deuterium substitution patterns, and pH-product ratios in the presence of added nucleophiles provide evidence for the following overlapping set of mechanisms for the hydrolysis of methanesulfonyl chloride (1) (in 0.1 M KCl at 25-degrees-C): (a) pH less-than-or-equal-to 1-6.7, reaction with water by direct nucleophilic attack on the sulfonyl chloride; (b) pH greater-than-or-equal-to 6.7-11.8, rate-determining attack by hydroxide anion to form sulfene (2), which is then trapped by water in a fast step; and (c) pH greater-than-or-equal-to 11.8, sulfene formation and sulfene trapping by hydroxide anion; careful inspection showed no sign of sulfene formation in the reaction with water or of direct displacement by hydroxide anion. This pattern, with appropriate variations in the values of pH(i) (the pH at which two competing mechanisms have the same rate), is apparently general for simple alkanesulfonyl chlorides having at least one hydrogen on the carbon bearing the sulfonyl group. Azide and acetate anions react with 1 below pH(i) for 1 (6.7) by direct nucleophilic substitution at the sulfur, but above pH(i) by trapping of the sulfene. 2-Chlorophenoxide anion reacts with 1 below pH 6.7 by both (a) direct displacement to form the ester and (b) elimination to form the sulfene. Above pH 6.7, sulfene is formed from the sulfonyl chloride by reaction with either 2-chlorophenoxide or hydroxide ion; this is followed by trapping of the sulfene with 2-chlorophenoxide, water, or hydroxide. The possibility of the 2-chlorophenoxide anion acting as a general base promoting the reaction of water with either 1 and 2 was examined, but no sign of either process was detected.

Kinetic and product ratio studies are consistent with the following mechanisms for the hydrolysis of methanesulfonyl chloride: (a) in acidic medium (pH 1–6) via a direct substitution on sulfur (SN 2-S), (b)in mildly basic medium (pH 8–10) by way of sulfene (CH2=SO2) formation followed by trapping with water, and (c) in strongly basic solution (pH > 10) via sulfene with trapping by the hydroxide ion. The reactions of primary and secondary alkanesulfonyl chlorides are qualitatively similar.

AbstractThe α,ω‐hydroxythiols (I) are chlorinated and then quenched with an equimolar amount of water to form the sultines (II).

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTGeometry dependence of the effect of a .beta.-substituent on the rate of hydrogen-deuterium exchange: evidence for a stereoelectronic component of the polar effectJ. F. King and Rajendra RathoreCite this: J. Am. Chem. Soc. 1990, 112, 5, 2001–2002Publication Date (Print):February 1, 1990Publication History Published online1 May 2002Published inissue 1 February 1990https://pubs.acs.org/doi/10.1021/ja00161a057https://doi.org/10.1021/ja00161a057research-articleACS PublicationsRequest reuse permissionsArticle Views88Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Ethenesulfonyl chloride (1) reacts with alcohols in the presence of tertiary amines to give a mixture of the alkyl ethenesulfonate (5) and the alkyl betylate (R3′N+CH2CH2SO2OR Cl−). With pyridine and neopentyl alcohol the product composition from the reaction of 1 is identical to that from the pyridinio-sulfonyl chloride (9). These results, when taken with experiments with deuterium labelled reagents, lead to the conclusion that the major (~80%) reaction pathway involves conversion of 1 or 9 to the sulfene 8, which reacts with the alcohol to form 5 or the betylate, and hence vinylogous nucleophilic catalysis is the major process leading to 5. The labelling experiments disclosed a minor pathway, evidently involving interconversion of 1 and 9. Examination of possible mechanisms leads to the suggestion that the sulfene is formed from 1 or 9 by way of the carbanion (14), i.e., that 9 reacts by an E1cB process, and that the minor pathway is simply the result of side reactions of the carbanion (14). Keywords: sulfenes, sulfonyl transfer mechanisms, vinylogous nucleophilic catalysis.

The hydrolysis of 2-hydroxyethanesulfonyl chloride (1) has been investigated with the aid of kinetic and product analysis studies. The results are quantitatively consistent with the mechanism of hydrolysis shown in Scheme 1, the chief features of which are (a) formation of β-sultone (2) and its rapid further reaction (the major pathway), together with (b) a minor direct hydrolysis route. The kinetics of both the β β-sultone formation and the direct hydrolysis shows two terms, one first order in 1 alone, and the other first order in hydroxide as well; the rates of the first- and second-order reactions are lowered by added sodium chloride. It is suggested (a) that the unimolecular β-sultone formation involves 1 in a complex with water (as in 9) and that the water acts as a general base in the cyclization to 2, and (b) the hydroxide-promoted reaction proceeds by cyclization of the conjugate base of 1 (i.e., 10). The unimolecular direct hydrolysis is regarded as a conventional hydrolysis of a sulfonyl chloride with attack of the water with general base assistance from a second water molecule. The hydroxide-promoted direct reaction in D2O leads to no uptake of deuterium, showing that the reaction does not go by way of the sulfene, and a reaction by way of a six-membered cyclic transition state is tentatively proposed. Evidence is presented that the chloride ion rate suppression is not primarily due to reaction of β-sultone with Cl− to give back 1; the possible origins of the effect are discussed. Keywords: sulfonyl chlorides, 2-hydroxyethanesulfonyl chloride, β-sultone, kinetics of sulfonyl chloride hydrolysis, mechanisms of sulfonyl chloride hydrolysis.

In accord with mechanistic prediction a one-pot, two-stage, controlled chlorination-hydrolysis of HO(CH2)nSH gave the sultine when n = 3 or 4, and the polymeric sulfinic ester when n = 5 or 6; alkaline hydrolysis of either product yielded the corresponding sodium ω-hydroxy-1-alkanesulfinate.