- Dithiocarboxylic Acids: An Old Theme Revisited and Augmented by New Preparative, Spectroscopic and Structural Facts
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The unstable dithiocarboxylic acids dithioacetic acid, 2-methyl-dithiopropionic acid, 2,2-dimethyl-dithiopropionic acid and dithiobenzoic acid were synthesized and characterized by NMR spectroscopy and GC/MS. The stable dithiocarboxylic acids 2,4,6-trimethyl benzoic acid, 2,4,6-tri-iso-propylbenzoic acid and 2,6-dimesityl benzoic acid were synthesized, isolated and characterized by spectroscopic methods and in parts by mass spectrometry and X-ray crystallography. The new data were used to re-evaluate literature data on the synthesis, spectroscopy and structural data of dithiocarboxylic acids as a fundamental class of organic compounds in general.
- Grote, Johanna,Friedrich, Felix,Berthold, Katarína,Hericks, Loreen,Neumann, Beate,Stammler, Hans-Georg,Mitzel, Norbert W.
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p. 2626 - 2633
(2018/02/06)
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- Mechanisms and rates of proton transfer to coordinated carboxydithioates: Studies on [Ni(S2CR){PhP(CH2CH2PPh2)2}]+ (R = Me, Et, Bun or Ph)
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The complexes [Ni(S2CR)(triphos)]BPh4 (R = Me, Et, Bun or Ph; triphos = PhP{CH2CH2PPh2}2) have been prepared and characterised. X-ray crystallography (for R = Et, Ph, C6H4Me-4, C6H4OMe-4 and C6H4Cl-4) shows that the geometry of the five-coordinate nickel in the cation is best described as distorted trigonal bipyramidal, containing a bidentate carboxydithioate ligand with the two sulfur atoms spanning axial and equatorial sites, the other axial site being occupied by the central phosphorus of triphos. The reactions of [Ni(S2CR)(triphos)]+ with mixtures of HCl and Cl- in MeCN to form equilibrium solutions containing [Ni(SH(S)CR)(triphos)]2+ have been studied using stopped-flow spectrophotometry. The kinetics show that proton transfer is slower than the diffusion-controlled limit and involves at least two coupled equilibria. The first step involves the rapid association between [Ni(S2CR)(triphos)]+ and HCl to form the hydrogen-bonded precursor, {[Ni(S2CR)(triphos)]+...HCl} (KR1) and this is followed by the intramolecular proton transfer (kR2) to produce [Ni(SH(S)CR)(triphos)]2+. In the reaction of [Ni(S2CMe)(triphos)]+ the rate law is consistent with the carboxydithioate ligand undergoing chelate ring-opening after protonation. It seems likely that chelate ring-opening occurs for all [Ni(S2CR)(triphos)]+, but only with [Ni(S2CMe)(triphos)]+ is the protonation step sufficiently fast that chelate ring-opening is rate-limiting. With all other systems, proton transfer is rate-limiting. DFT calculations indicate that protonation can occur at either sulfur atom, but only protonation at the equatorial sulfur results in chelate ring-opening. The ways in which protonation of either sulfur atom complicates the analyses and interpretation of the kinetics are discussed. This journal is
- Alwaaly, Ahmed,Clegg, William,Henderson, Richard A.,Probert, Michael R.,Waddell, Paul G.
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p. 3307 - 3317
(2015/03/05)
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- Thiocarbonylthio compounds (S=C(Z)S-R) in free radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization). Effect of the activating Group Z
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Free-radical polymerization in the presence of suitable addition-fragmentation chain transfer agents [S=C(Z)S-R] (RAFT agents) possess the characteristics of a living polymerization (i.e., polymer products can be reactivated for chain extension and/or block synthesis, molecular weights are predetermined by RAFT agent concentration and conversion, narrow polydispersities are possible). Styrene polymerizations (110°C, thermal initiation) were performed for two series of RAFT agents [S=C(Z)S-CH2Ph and S=C(Z)S-C(Me)2CN]. The chain transfer coefficients decrease in the series where Z is Ph > SCH2Ph ~ SMe ~ Me ~ N-pyrrolo ? OC6F5 > N-lactam > OC6H5 > O(alkyl) ? N(alkyl)2 (only the first five in this series provide narrow polydispersity polystyrene ( trithiocarbonates ~ dithioalkanoates > dithiocarbonates (xanthates) > dithiocarbamates. However, electron-withdrawing substituents on Z can enhance the activity of RAFT agents to modify the above order. Thus, substituents that render the oxygen or nitrogen lone pair less available for delocalization with the C=S can substantially enhance the effectiveness of xanthates or dithiocarbamates, respectively. The trend in relative effectiveness of the RAFT agents is rationalized in terms of interaction of Z with the C=S double bond to activate or deactivate that group toward free radical addition. Molecular orbital calculations and the estimated LUMO energies of the RAFT agents can be used in a qualitative manner to predict the effect of the Z substituent on the activity of RAFT agents.
- Chiefari, John,Mayadunne, Roshan T.A.,Moad, Catherine L.,Moad, Graeme,Rizzardo, Ezio,Postma, Almar,Skidmore, Melissa A.,Thang, San H.
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p. 2273 - 2283
(2007/10/03)
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- Dithio and Thiono Esters, 59. - Reactions of Aliphatic Dithio Acid Dianions with Carbon Disulfide
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Dianions 2 of dithioacids 1 and carbon disulfide yield in a kinetically controlled reaction at -78 deg C S-adducts (e.g. 3, 13) or in a thermodynamically controlled reaction at room temperatur C-adducts .Acidification of 10 and subsequent reactions give rise to the tetrathiomalonic acids 18 and its derivatives 19 with 2,6,9,10-tetrathiaadamantane structure.Deprotonation of 10a leads to the tetrathiomalonic acid tetraanion (20) which may be alkylated to yield the tetrakis(alkylthio)allenes 21.By condensation of the dithioacid dianions 2, the tetrathiomalonic acid trianion 10 and the tetrathiomalonic a cid tetraanion (20) with 2,3-dichloro-1,4-naphthoquinone (32) a number of naphtho-1,3-dithiole-4,9-diones (e.g. 33, 35, 37) are obtained. - Key Words: Dithio acid dianions / Tetrathiomalonic acid / Anions / Tetrathiomalonic acid tetraanion / Dithioacrylic esters / Thio acids / Allenes, alkylthio- / Naphtho-1,3-dithiole-4,9-diones / Malonic acid, tetrathio- / Acrylic acid, dithio
- Hartke, Klaus,Rettberg, Norbert,Dutta, Dinah,Gerber, Hans-Dieter
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p. 1081 - 1090
(2007/10/02)
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- Diastereoselectivity of the thio-Claisen rearrangement of acyclic precursors bearing a chiral centre adjacent to carbon 6
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A number of chiral allylic alcohols have been prepared and submitted to a Mitsunobu reaction with dithioacetic acid. Allyl dithioesters were deprotonated by LDA at -30°C and resulting enethiolates were quenched with iodomethane to afford quantitatively S-
- Desert, Stephane,Metzner, Patrick
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p. 10327 - 10338
(2007/10/02)
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- NEW ASPECTS OF DITHIO AND THIONO ESTERS
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The field of dithio and thiono esters is expanding rapidly.Therefore emphasis is layed mainly on results obtained by the reasearch group of the author.In agreement with theoretical considerations thiono esters are always more stable than dithio esters.In the preparation of dithio and thiono esters by thiolysis slightly acidic conditions were found to be essential.The CH-acidity at the α-carbon of dithio and thiono esters with pKa values about 12 is comparable to that of classical CH-acidic compounds such as acetoacetic ester.Dithiono and tetrathio malonates do not show the expected chemistry of malonic esters; the electrophile reacts preferentially at the sulfur atom. α,β-Unsaturated dithio and thiono esters have been prepared by Wittig-Horner reactions, by Peterson synthesis, and by aldol condensations. α,β-Acetylenic dithio and thiono esters were obtained for the first time.In the formation of thiopeptide bonds from α-amino dithio esters the racemization observed seems to be of fundamental importance.Dianions of dithio acids were found to condense with different electrophiles.
- Hartke, Klaus
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p. 223 - 253
(2007/10/02)
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- Pesticidal compositions containing phosphoric esters and divalent sulphur compounds
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Pesticidal composition comprising: a pesticidal, phosphoric ester the molecule of which has at least one alkyl group of 1 to 3 carbon atoms, 0.05 to 10% of an agent stabilizing the said ester against decomposition by protonisation, together with adjuvants characterized in that the stabilizing agent comprises at least one sulphur compound containing per molecule at least one divalent sulphur atom of which one valence is bonded to an atom chosen from sulphur, carbon, nitrogen, hydrogen, and metals capable of giving a salt, the other valence being bonded to an atom chosen from hydrogen, the carbon atom already noted, a second carbon atom, the nitrogen atom already noted, a second nitrogen atom, the metal atom already noted in the case of a metal of valence greater than one, a second atom of metal and oxygen when the first valence is not attached to an atom of hydrogen, the proportion of sulphur calculated with reference to the weight of the sulphur compound being between 5 and 99%. Process for stabilizing a phosphoric ester of which the molecule possesses at least one alkyl group containing 1 to 3 carbon atoms characterized in that there is added to the phosphoric ester or to a mixture which contains it, 0.05 to 10% calculated on the weight of the phosphoric acid ester of an agent capable of stabilizing the said phosphoric ester against protonisation and comprising at least one sulphur compound such as that defined thereupon.
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