|
BINAP 3D
BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) is an organophosphorus compound. This chiral diphosphine ligand is widely used in asymmetric synthesis. It consists of a pair of 2-diphenylphosphinonaphthyl groups linked at the 1 and 1′ positions. This C2-symmetric framework lacks a stereogenic atom, but has axial chirality due to restricted rotation (atropisomerism). The barrier to racemization is high due to steric hindrance, which limits rotation about the bond linking the naphthyl rings. The dihedral angle between the naphthyl groups is approximately 90°. The natural bite angle is 93°. Use as ligand in asymmetric catalysis BINAP is used in organic synthesis for enantioselective transformations catalyzed by its complexes of ruthenium, rhodium, and palladium. As pioneered by Ryōji Noyori and his co-workers, rhodium complexes of BINAP are useful for the synthesis of (–)-menthol. Silver complexes are also important; BINAP- AgF can be used to enantioselectiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BINAP 3D
BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) is an organophosphorus compound. This chiral diphosphine ligand is widely used in asymmetric synthesis. It consists of a pair of 2-diphenylphosphinonaphthyl groups linked at the 1 and 1′ positions. This C2-symmetric framework lacks a stereogenic atom, but has axial chirality due to restricted rotation (atropisomerism). The barrier to racemization is high due to steric hindrance, which limits rotation about the bond linking the naphthyl rings. The dihedral angle between the naphthyl groups is approximately 90°. The natural bite angle is 93°. Use as ligand in asymmetric catalysis BINAP is used in organic synthesis for enantioselective transformations catalyzed by its complexes of ruthenium, rhodium, and palladium. As pioneered by Ryōji Noyori and his co-workers, rhodium complexes of BINAP are useful for the synthesis of (–)-menthol. Silver complexes are also important; BINAP- AgF can be used to enantioselectiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Complex (chemistry)
A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many metal-containing compounds, especially those that include transition metals (elements like titanium that belong to the Periodic Table's d-block), are coordination complexes. Nomenclature and terminology Coordination complexes are so pervasive that their structures and reactions are described in many ways, sometimes confusingly. The atom within a ligand that is bonded to the central metal atom or ion is called the donor atom. In a typical complex, a metal ion is bonded to several donor atoms, which can be the same or different. A polydentate (multiple bonded) ligand is a molecule or ion that bonds to the central atom through several of the ligand's atoms; ligands with 2, 3, 4 or even 6 bonds to the central atom are common. These compl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SEGPHOS
SEGPHOS is a chiral ligand developed by Takasago that is used in asymmetric synthesis. It was developed after BINAP BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) is an organophosphorus compound. This chiral diphosphine ligand is widely used in asymmetric synthesis. It consists of a pair of 2-diphenylphosphinonaphthyl groups linked at the 1 and 1 ... and was investigated since it has a narrower dihedral angle between the aromatic faces. This was predicted and then confirmed to increase the enantioselectivity and activity of metal complexes of SEGPHOS. After its commercialization, SEGPHOS and its substituted derivatives have been found to constitute a privileged ligand class for a variety of transition metal catalysts and chemical transformations beyond its original application in ruthenium-catalyzed enantioselective hydrogenation. In addition to the parent ligand bearing phenyl groups on the phosphorus atoms, the bulkier derivatives DM-SEGPHOS and DTBM-SEGPHOS ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diphosphine
Diphosphane, or diphosphine, is an inorganic compound with the chemical formula P2H4. This colourless liquid is one of several binary phosphorus hydrides. It is the impurity that typically causes samples of phosphine to ignite in air. Properties, preparation, reactions Diphosphane adopts the gauche conformation (like hydrazine, less symmetrical than shown in the image) with a P−P distance of 2.219 angstroms. It is nonbasic, unstable at room temperature, and Pyrophoricity, spontaneously flammable in air. It is only poorly soluble in water but dissolves in organic solvents. Its 1H NMR spectrum consists of 32 lines resulting from an A2XX'A'2 splitting system. Diphosphane is produced by the hydrolysis of calcium monophosphide, which can be described as the Ca2+ derivative of . According to an optimized procedure, hydrolysis of 400 g of CaP at −30 °C gives about 20 g of product, slightly contaminated with phosphine. Reaction of diphosphane with butyllithium affords a varie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silyl Enol Ether
Silyl enol ethers in organic chemistry are a class of organic compounds that share a common functional group composed of an enolate bonded through its oxygen end to an organosilicon group. They are important intermediates in organic synthesis. Synthesis Silyl enol ethers are generally prepared by reacting an enolizable Carbonyl group, carbonyl compound with a silyl electrophile and a Base (chemistry), base, or just reacting an enolate with a silyl electrophile.Clayden, J., Greeves, N., & Warren, S. (2012). Silyl enol ethers. In ''Organic chemistry'' (Second ed., pp. 466-467). Oxford University Press. Since silyl electrophiles are HSAB theory, hard and silicon-oxygen bonds are very strong, the oxygen (of the carbonyl compound or enolate) acts as the nucleophile to form a Si-O single bond. The most commonly used silyl electrophile is trimethylsilyl chloride. To increase the rate of reaction, trimethylsilyl triflate may also be used in the place of trimethylsilyl chloride as a more el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stereoselectivity
In chemistry, stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non- stereospecific creation of a new stereocenter or during a non-stereospecific transformation of a pre-existing one. The selectivity arises from differences in steric and electronic effects in the mechanistic pathways leading to the different products. Stereoselectivity can vary in degree but it can never be total since the activation energy difference between the two pathways is finite. Both products are at least possible and merely differ in amount. However, in favorable cases, the minor stereoisomer may not be detectable by the analytic methods used. An enantioselective reaction is one in which one enantiomer is formed in preference to the other, in a reaction that creates an optically active product from an achiral starting material, using either a chiral catalyst, an enzyme or a chiral reagent. The degree of selectivity is meas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silver(I) Fluoride
Silver(I) fluoride is the inorganic compound with the formula AgF. It is one of the three main fluorides of silver, the others being silver subfluoride and silver(II) fluoride. AgF has relatively few niche applications; it has been employed as a fluorination and desilylation reagent in organic synthesis and in aqueous solution as a topical caries treatment in dentistry. The hydrates of AgF present as colourless, while pure anhydrous samples are yellow. Preparation High-purity silver(I) fluoride can be produced by the heating of silver carbonate to under a hydrogen fluoride environment, in a platinum tube: :Ag2CO3 + 2 HF -> 2 AgF + H2O + CO2 Laboratory routes to the compound typically avoid the use of gaseous hydrogen fluoride. One method is the thermal decomposition of silver tetrafluoroborate: :AgBF4 -> AgF + BF3 In an alternative route, silver(I) oxide is dissolved in concentrated aqueous hydrofluoric acid, and the silver fluoride is precipitated out of the resulti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earth's crust in the pure, free elemental form ("native silver"), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc Refining (metallurgy), refining. Silver has long been valued as a precious metal. Silver metal is used in many bullion coins, sometimes bimetallism, alongside gold: while it is more abundant than gold, it is much less abundant as a native metal. Its purity is typically measured on a per-mille basis; a 94%-pure alloy is described as "0.940 fine". As one of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nippon Kagaku Kaishi
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north toward the East China Sea, Philippine Sea, and Taiwan in the south. Japan is a part of the Ring of Fire, and spans an archipelago of 6852 islands covering ; the five main islands are Hokkaido, Honshu (the "mainland"), Shikoku, Kyushu, and Okinawa. Tokyo is the nation's capital and largest city, followed by Yokohama, Osaka, Nagoya, Sapporo, Fukuoka, Kobe, and Kyoto. Japan is the eleventh most populous country in the world, as well as one of the most densely populated and urbanized. About three-fourths of the country's terrain is mountainous, concentrating its population of 123.2 million on narrow coastal plains. Japan is divided into 47 administrative prefectures and eight traditional regions. The Greater Tokyo Area is the mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chirality Ind
Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from its mirror image; that is, it cannot be superimposed onto it. Conversely, a mirror image of an ''achiral'' object, such as a sphere, cannot be distinguished from the object. A chiral object and its mirror image are called ''enantiomorphs'' (Greek, "opposite forms") or, when referring to molecules, ''enantiomers''. A non-chiral object is called ''achiral'' (sometimes also ''amphichiral'') and can be superposed on its mirror image. The term was first used by Lord Kelvin in 1893 in the second Robert Boyle Lecture at the Oxford University Junior Scientific Club which was published in 1894: Human hands are perhaps the most recognized example of chirality. The left hand is a non-superimposable mirror image of the right hand; no matter how th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Menthol
Menthol is an organic compound, more specifically a monoterpenoid, made synthetically or obtained from the oils of corn mint, peppermint, or other mints. It is a waxy, clear or white crystalline substance, which is solid at room temperature and melts slightly above. The main form of menthol occurring in nature is (−)-menthol, which is assigned the (1''R'',2''S'',5''R'') configuration. Menthol has local anesthetic and counterirritant qualities, and it is widely used to relieve minor throat irritation. Menthol also acts as a weak κ-opioid receptor agonist. Structure Natural menthol exists as one pure stereoisomer, nearly always the (1''R'',2''S'',5''R'') form (bottom left corner of the diagram below). The eight possible stereoisomers are: : In the natural compound, the isopropyl group is in the ''trans'' orientation to both the methyl and hydroxyl groups. Thus, it can be drawn in any of the ways shown: : The (+)- and (−)-enantiomers of menthol are the most stable among ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ryōji Noyori
is a Japanese chemist. He won the Nobel Prize in Chemistry in 2001, Noyori shared a half of the prize with William S. Knowles for the study of chirally catalyzed hydrogenations; the second half of the prize went to K. Barry Sharpless for his study in chirally catalyzed oxidation reactions (Sharpless epoxidation). Education and career Ryōji Noyori was born in Kobe, Japan. Early in his school days Ryoji was interested in physics. His interest was kindled by the famous physicist Hideki Yukawa (1949 Nobel Prize in Physics winner), a close friend of his father. Later, he became fascinated with chemistry, after hearing a presentation on nylon at an industrial exposition. He saw the power of chemistry as being the ability to "produce high value from almost nothing". He was a student at the School of Engineering (Department of Industrial Chemistry) of the Kyoto University, where he graduated in 1961. He subsequently obtained a Master's degree in Industrial Chemistry from the Gradua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
