Thus, treatment of 56a with excess n-BuLi followed by quenching with MeI afforded the monoalkylated bicycle 134. Oxadiazolinethiones (25b; R = H, Me or Ph) are stronger acids, having pKa values (water) of 3.85, 4.45 and 4.27 respectively. In the case of oxathiazoline (167) dehydrochlorination affords the azonylene derivative (168) (Scheme 27) 〈85JCS(P1)1517〉. From: Comprehensive Heterocyclic Chemistry II, 1996, I. Shcherbakova, A.F.
Mechanism of the acid-catalyzed α-halogenation (Fig. Deprotonation [carboxylate formation] Deprotonation [carboxylate formation] Definition: When treated with base, carboxylic acids form carboxylate salts. Generation of NHC from imidazo[1,5-a]pyridinium ions, Christopher G. Barber, in Comprehensive Organic Functional Group Transformations, 1995. However, it has been confirmed 〈92JA5591〉 that nucleophilic attack of the hydroxide ion on the dioxetane peroxide bond is preferred over the Kornblum–De La Mare reaction, at least for 3,3-disubstituted dioxetanes (see transformation 9 in Scheme 46).
stream In this mechanism, an alcohol is added to a carboxylic acid by the following steps: 1. The metal carbonyl complex formed by reaction of tri(phenylethynyl) antimony with dicobaltoctacarbonyl as described in the arsine case, has been fully characterised, but the interesting dimer (1) could not be obtained for the antimony case. A proton is lost from the oxonium ion generated in Step 2. Deprotonation occurs selectively alpha to a carbanion-stabilizing substituent to provide benzyl, allyl, propargyl, and thiophenyl stabilized anions. Physical Properties: The polar nature of both the O-H and C=O bonds (due to the electonegativity difference of the atoms) results in the formation of strong hydrogen bonds with other carboxylic acid molecules or other H-bonding systems (e.g. Deprotonation of a dihydrothiazine ring, followed by a reaction with an electrophile, is most straightforward in benzothiazin-3-ones (general structure 35), which are deprotonated at the 2-position by lithium diisopropyl amide (LDA). Attempted cheleotropic extrusion of SO2 of the product 134, described in Section 13.03.5.2, produced many products in low yield. Table 7 summarizes some carbenes possessing this heterocyclic skeleton that have been prepared through this manner, and, in some cases, directly used for the preparation of various complexes. Deprotonation of 1,3,4-dioxazolines (166) with a strong base (ButOK) results in ring fragmentation to give nitriles and the carboxylate anion 〈72CB2805, 91SL189〉, which in turn is converted to carboxylic acid derivatives. By continuing you agree to the use of cookies. When imidazolinium ions are treated with a base, deprotonation then occurs at C-3 to give carbenes.
Oxadiazolin-5-ones (25a) and -5-thiones (25b) are weak acids and formally undergo deprotonation at the NH group. Nikolaos G. Argyropoulos, in Comprehensive Heterocyclic Chemistry II, 1996. 2. S. Yamazaki, in Comprehensive Heterocyclic Chemistry III, 2008. Recently, the first phosphothiolate-mercaptophosphonate [1,2]-sigmatropic rearrangement was reported via α-deprotonation of a phosphorothiolate (Scheme 56) <1998T1523>. Deprotonation of salt 103a with ButOK gave the dimeric product 106 in 84% yield, a ‘higher analogue’ of TTF, probably arising from initial generation of the carbenic intermediate 105, a valence isomer of intermediate 104 (see Scheme 12) <1996CC205> and <1996BCJ2349>. The carboxyl carbon of the carboxylic acid is protonated.
Table 7.
For example, the reaction of t-butyl-β-chlorohydroperoxide (24) with sodium hydroxide in aqueous methanol afforded the 2-methylpropane-1,2-diol (Scheme 48). J. Hill, in Comprehensive Heterocyclic Chemistry, 1984. Important examples include the amino acids and fatty acids.Deprotonation of a carboxylic acid gives a carboxylate anion When S-oxide analogues were reacted similarly with LDA, 2-deprotonation competed with 3-deprotonation (Scheme 35) and two products were obtained upon reaction with MeI <1984J(P1)1949>. Deprotonation of ethynyl derivatives, generally to form the magnesium derivative, permits efficient condensation with aldehydes and ketones, for example, to yield the hydroxyalkyl compounds. These compounds were found to be excellent C-ligands for transition metals.
ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. URL: https://www.sciencedirect.com/science/article/pii/B0080446558000258, URL: https://www.sciencedirect.com/science/article/pii/B9780080449920007094, URL: https://www.sciencedirect.com/science/article/pii/B9780080965192000916, URL: https://www.sciencedirect.com/science/article/pii/B9780080449920010105, URL: https://www.sciencedirect.com/science/article/pii/B0080447058002132, URL: https://www.sciencedirect.com/science/article/pii/B9780080965185000332, URL: https://www.sciencedirect.com/science/article/pii/B9780080449920011111, URL: https://www.sciencedirect.com/science/article/pii/B0080447058002405, URL: https://www.sciencedirect.com/science/article/pii/B9780080449920012037, URL: https://www.sciencedirect.com/science/article/pii/B9780080965185000927, Comprehensive Heterocyclic Chemistry II, 1996, Synthesis: Carbon With One Heteroatom Attached by a Single Bond, Comprehensive Organic Functional Group Transformations II, Six-membered Rings with Two Heteroatoms, and their Fused Carbocyclic Derivatives, Bicyclic 5-5 and 5-6 Fused Ring Systems with at least One Bridgehead (Ring Junction) N, Synthesis: Carbon with Two Heteroatoms, Each Attached by a Single Bond, Comprehensive Organic Functional Group Transformations, Four-membered Rings, with all Fused Systems containing Four-membered Rings, Five- and Six-membered Fused Systems with Bridgehead (Ring Junction) Heteroatoms concluded: 6-6 Bicyclic with One or Two N or Other Heteroatoms; Polycyclic; Spirocyclic, Synthesis: Carbon with One Heteroatom Attached by a Single Bond, Seven-membered Heterocyclic Rings and their Fused Derivatives, Five-membered Rings with More than Two Heteroatoms and Fused Carbocyclic Derivatives.