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Thioacetal
In organosulfur chemistry, thioacetals are the sulfur (''thio-'') analogues of acetals (). There are two classes: the less-common monothioacetals, with the formula , and the dithioacetals, with the formula (symmetric dithioacetals) or (asymmetric dithioacetals). The symmetric dithioacetals are relatively common. They are prepared by condensation of thiols () or dithiols (two groups) with aldehydes (). These reactions proceed via the intermediacy of hemithioacetals (): #Thiol addition to give hemithioacetal: #::RSH + R'CH(O) -> R'CH(SR)OH #Thiol addition with loss of water to give dithioacetal: #::RSH + R'CH(OH)SR -> R'CH(SR)2 + H2O Such reactions typically employ either a Lewis acid or Brønsted acid as catalyst. Dithioacetals generated from aldehydes and either 1,2-ethanedithiol or 1,3-propanedithiol are especially common among this class of molecules for use in organic synthesis.P. Stütz And P. A. Stadler "3-alkylated And 3-acylated Indoles From A Common Precurs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organosulfur Chemistry
Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature abounds with organosulfur compounds—sulfur is vital for life. Of the 20 common amino acids, two (cysteine and methionine) are organosulfur compounds, and the antibiotics penicillin and sulfa drugs both contain sulfur. While sulfur-containing antibiotics save many lives, sulfur mustard is a deadly chemical warfare agent. Fossil fuels, coal, petroleum, and natural gas, which are derived from ancient organisms, necessarily contain organosulfur compounds, the removal of which is a major focus of oil refineries. Sulfur shares the chalcogen group with oxygen, selenium, and tellurium, and it is expected that organosulfur compounds have similarities with carbon–oxygen, carbon–selenium, and carbon–tellurium compounds. A classical chemical test for the detection of sulfur compounds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thioketal
In organosulfur chemistry, a thioketal is the sulfur analogue of a ketal (), with one of the oxygen replaced by sulfur (as implied by the ''thio-'' prefix), giving the structure . A dithioketal has ''both'' oxygens replaced by sulfur (). Thioketals can be obtained by reacting ketones () or aldehydes () with thiols (). An oxidative cleavage mechanism has been proposed for dithioketals, which involves thioether oxidation, the formation of thionoiums, and hydrolysis, resulting in the formation of aldehyde and ketone products. Thioketal moieties are found to be responsive to reactive oxygen species In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. The reduction of molecular oxygen () p ... (ROS). In the presence of ROS, thioketals can be selectively cleaved. ROS successfully cleave heterobifunctional thioketal linkers, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thioacetal
In organosulfur chemistry, thioacetals are the sulfur (''thio-'') analogues of acetals (). There are two classes: the less-common monothioacetals, with the formula , and the dithioacetals, with the formula (symmetric dithioacetals) or (asymmetric dithioacetals). The symmetric dithioacetals are relatively common. They are prepared by condensation of thiols () or dithiols (two groups) with aldehydes (). These reactions proceed via the intermediacy of hemithioacetals (): #Thiol addition to give hemithioacetal: #::RSH + R'CH(O) -> R'CH(SR)OH #Thiol addition with loss of water to give dithioacetal: #::RSH + R'CH(OH)SR -> R'CH(SR)2 + H2O Such reactions typically employ either a Lewis acid or Brønsted acid as catalyst. Dithioacetals generated from aldehydes and either 1,2-ethanedithiol or 1,3-propanedithiol are especially common among this class of molecules for use in organic synthesis.P. Stütz And P. A. Stadler "3-alkylated And 3-acylated Indoles From A Common Precurs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mozingo Reduction
The Mozingo reduction, also known as Mozingo reaction or thioketal reduction, is a chemical reaction capable of fully reducing a ketone or aldehyde to the corresponding alkane via a dithioacetal. The reaction scheme is as follows: The ketone or aldehyde is activated by conversion to cyclic dithioacetal by reaction with a dithiol (nucleophilic substitution) in presence of a H+ donating acid. The cyclic dithioacetal structure is then hydrogenolyzed using Raney nickel. Raney nickel is converted irreversibly to nickel sulfide. This method is milder than either the Clemmensen or Wolff-Kishner reductions, which employ strongly acidic or basic conditions, respectively, that might interfere with other functional groups. History The reaction is named after Ralph Mozingo, who reported the cleavage of thioether In organic chemistry, an organic sulfide (British English sulphide) or thioether is an organosulfur functional group with the connectivity as shown on right. Like many o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dithioacetal
In organosulfur chemistry, thioacetals are the sulfur (''thio-'') analogues of acetals (). There are two classes: the less-common monothioacetals, with the formula , and the dithioacetals, with the formula (symmetric dithioacetals) or (asymmetric dithioacetals). The symmetric dithioacetals are relatively common. They are prepared by condensation of thiols () or dithiols (two groups) with aldehydes (). These reactions proceed via the intermediacy of hemithioacetals (): #Thiol addition to give hemithioacetal: #::RSH + R'CH(O) -> R'CH(SR)OH #Thiol addition with loss of water to give dithioacetal: #::RSH + R'CH(OH)SR -> R'CH(SR)2 + H2O Such reactions typically employ either a Lewis acid or Brønsted acid as catalyst. Dithioacetals generated from aldehydes and either 1,2-ethanedithiol or 1,3-propanedithiol are especially common among this class of molecules for use in organic synthesis.P. Stütz And P. A. Stadler "3-alkylated And 3-acylated Indoles From A Common Precurso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetal
In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments not hydrogen. The two R' groups can be equivalent to each other (a "symmetric acetal") or not (a "mixed acetal"). Acetals are formed from and convertible to aldehydes or ketones and have the same oxidation state at the central carbon, but have substantially different chemical stability and reactivity as compared to the analogous carbonyl compounds. The central carbon atom has four bonds to it, and is therefore saturated and has tetrahedral geometry. The term ketal is sometimes used to identify structures associated with ketones (both R groups organic fragments rather than hydrogen) rather than aldehydes and, historically, the term acetal was used specifically for the aldehyde-related cases (having at least one hydrogen in place of an R on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dithioacetal Synthesis V
In organosulfur chemistry, thioacetals are the sulfur (''thio-'') analogues of acetals (). There are two classes: the less-common monothioacetals, with the formula , and the dithioacetals, with the formula (symmetric dithioacetals) or (asymmetric dithioacetals). The symmetric dithioacetals are relatively common. They are prepared by condensation of thiols () or dithiols (two groups) with aldehydes (). These reactions proceed via the intermediacy of hemithioacetals (): #Thiol addition to give hemithioacetal: #::RSH + R'CH(O) -> R'CH(SR)OH #Thiol addition with loss of water to give dithioacetal: #::RSH + R'CH(OH)SR -> R'CH(SR)2 + H2O Such reactions typically employ either a Lewis acid or Brønsted acid as catalyst. Dithioacetals generated from aldehydes and either 1,2-ethanedithiol or 1,3-propanedithiol are especially common among this class of molecules for use in organic synthesis.P. Stütz And P. A. Stadler "3-alkylated And 3-acylated Indoles From A Common Precurso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1,3-propanedithiol
1,3-Propanedithiol is the chemical compound with the formula HSCH2CH2CH2SH. This dithiol is a useful reagent in organic synthesis. This liquid, which is readily available commercially, has an intense stench. Use in organic synthesis 1,3-Propanedithiol is mainly used for the protection of aldehydes and ketones via their reversible formation of dithianes. A prototypical reaction is its formation of 1,3-dithiane from formaldehyde. The reactivity of this dithiane illustrates the concept of umpolung. Alkylation gives thioethers, e.g. 1,5-dithiacyclooctane. The unpleasant odour of 1,3-propanedithiol has encouraged the development of alternative reagents that generate similar derivatives. 1,3-Propanedithiol is used in the synthesis of tiapamil. Use in inorganic synthesis 1,3-Propanedithiol reacts with metal ions to form chelate rings. Illustrative is the synthesis of the derivative diiron propanedithiolate hexacarbonyl upon reaction with triiron dodecacarbonyl: :Fe3(CO)12 + C3H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nucleophile
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are Lewis bases. ''Nucleophilic'' describes the affinity of a nucleophile to bond with positively charged atomic nuclei. Nucleophilicity, sometimes referred to as nucleophile strength, refers to a substance's nucleophilic character and is often used to compare the affinity of atoms. Neutral nucleophilic reactions with solvents such as alcohols and water are named solvolysis. Nucleophiles may take part in nucleophilic substitution, whereby a nucleophile becomes attracted to a full or partial positive charge, and nucleophilic addition. Nucleophilicity is closely related to basicity. History The terms ''nucleophile'' and '' electrophile'' were introduced by Christopher Kelk Ingold in 1933, replacing the terms ''anionoid'' and ''catio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrophilic
In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carries a partial positive charge, or have an atom that does not have an octet of electrons. Electrophiles mainly interact with nucleophiles through addition and substitution reactions. Frequently seen electrophiles in organic syntheses include cations such as H+ and NO+, polarized neutral molecules such as HCl, alkyl halides, acyl halides, and carbonyl compounds, polarizable neutral molecules such as Cl2 and Br2, oxidizing agents such as organic peracids, chemical species that do not satisfy the octet rule such as carbenes and radicals, and some Lewis acids such as BH3 and DIBAL. Organic chemistry Addition of halogens These occur between alkenes and electrophiles, often halogens as in halogen addition reactions. Common re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1,3-dithiane
A dithiane is a heterocyclic compound composed of a cyclohexane core structure wherein two methylene bridges (-- units) are replaced by sulfur centres. The three isomeric parent heterocycles are 1,2-dithiane, 1,3-dithiane and 1,4-dithiane. 1,3-Dithianes 1,3-Dithianes are protecting group of some carbonyl-containing compounds due to their inertness to many conditions. They form by treatment of the carbonyl compound with 1,3-propanedithiol under conditions that remove water from the system. The protecting group can be removed with mercuric reagents, a process that exploits the high affinity of Hg(II) for thiolates. 1,3-Dithianes are also employed in umpolung reactions, such as the Corey–Seebach reaction:T. W. Green, P. G. M. Wuts, "Protective Groups in Organic Synthesis" Wiley-Interscience, New York, 1999. . : Typically, in organic synthesis, ketones and aldehydes are protected as their dioxolane Dioxolane is a heterocyclic acetal with the chemical formula (CH2)2O2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protective Group
A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In many preparations of delicate organic compounds, some specific parts of their molecules cannot survive the required reagents or chemical environments. Then, these parts, or groups, must be protected. For example, lithium aluminium hydride is a highly reactive but useful reagent capable of reducing esters to alcohols. It will always react with carbonyl groups, and this cannot be discouraged by any means. When a reduction of an ester is required in the presence of a carbonyl, the attack of the hydride on the carbonyl has to be prevented. For example, the carbonyl is converted into an acetal, which does not react with hydrides. The acetal is then called a protecting group for the carbonyl. After the step involving the hydride is complete, the ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
