In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom to the substrates in synthetic steps, through nucleophilic addition or simple deprotonation. Organolithium reagents are used in industry as an initiator for anionic polymerization, which leads to the production of various elastomers. They have also been applied in asymmetric synthesis in the pharmaceutical industry. Due to the large difference in electronegativity between the carbon atom and the lithium atom, the C−Li bond is highly ionic. Owing to the polar nature of the C−Li bond, organolithium reagents are good nucleophiles and strong bases. For laboratory organic synthesis, many organolithium reagents are commercially available in solution form. These reagents are highly reactive, and are sometimes pyrophoric.
As the name suggests, a non-nucleophilic base is a sterically hindered organic base that is a poor nucleophile. Normal bases are also nucleophiles, but often chemists seek the proton-removing ability of a base without any other functions. Typical non-nucleophilic bases are bulky, such that protons can attach to the basic center but alkylation and complexation is inhibited.
n-Butyllithium C4H9Li (abbreviated n-BuLi) is an organolithium reagent. It is widely used as a polymerization initiator in the production of elastomers such as polybutadiene or styrene-butadiene-styrene (SBS). Also, it is broadly employed as a strong base (superbase) in the synthesis of organic compounds as in the pharmaceutical industry.
A superbase is a compound that has a particularly high affinity for protons. Superbases are of theoretical interest and potentially valuable in organic synthesis. Superbases have been described and used since the 1850s.
Sodium bis(trimethylsilyl)amide is the organosilicon compound with the formula NaN(Si 3)2. This species, usually called NaHMDS, is a strong base used for deprotonation reactions or base-catalyzed reactions. Its advantages are that it is commercially available as a solid and it is soluble not only in ethers, such as THF or diethyl ether, but also in aromatic solvents, like benzene and toluene by virtue of the lipophilic TMS groups.
tert-Butyllithium is a chemical compound with the formula (CH3)3CLi. As an organolithium compound, it has applications in organic synthesis since it is a strong base, capable of deprotonating many carbon molecules, including benzene. tert-Butyllithium is available commercially as hydrocarbon solutions; it is not usually prepared in the laboratory.
Di-tert-butyl dicarbonate is a reagent widely used in organic synthesis. Since this compound can be regarded formally as the acid anhydride derived from a tert-butoxycarbonyl (Boc) group, it is commonly referred to as Boc anhydride. This pyrocarbonate reacts with amines to give N-tert-butoxycarbonyl or so-called Boc derivatives. These carbamate derivatives do not behave as amines, which allows certain subsequent transformations to occur that would be incompatible with the amine functional group. The Boc group can later be removed from the amine using moderately strong acids. Thus, Boc serves as a protective group, for instance in solid phase peptide synthesis. Boc-protected amines are unreactive to most bases and nucleophiles, allowing for the use of the fluorenylmethyloxycarbonyl group (Fmoc) as an orthogonal protecting group.
Di-tert-butyl peroxide or DTBP is an organic compound consisting of a peroxide group bonded to two tert-butyl groups. It is one of the most stable organic peroxides, due to the tert-butyl groups being bulky. It is a colorless liquid.
Directed ortho metalation (DoM) is an adaptation of electrophilic aromatic substitution in which electrophiles attach themselves exclusively to the ortho- position of a direct metalation group or DMG through the intermediary of an aryllithium compound. The DMG interacts with lithium through a hetero atom. Examples of DMG's are the methoxy group, a tertiary amine group and an amide group.The compound can be produced by directed lithiation of anisole.
The tert-butyloxycarbonyl protecting group or tert-butoxycarbonyl protecting group is a protecting group used in organic synthesis.
Di-tert-butylzinc is a compound with the formula ZnC8H18. This compound is used as a meta activating reagent in the syntheses of N,N-dimethyl-3-iodoaniline from N,N-dimethylaniline.
sec-Butyllithium is an organometallic compound with the formula CH3CHLiCH2CH3, abbreviated sec-BuLi or s-BuLi. This chiral organolithium reagent is used as a source of sec-butyl carbanion in organic synthesis.
EuFOD is the chemical compound with the formula Eu(OCC(CH3)3CHCOC3F7)3, also called Eu(fod)3. This coordination compound is used primarily as a shift reagent in NMR spectroscopy. It is the premier member of the lanthanide shift reagents and was popular in the 1970s and 1980s.
The Jones oxidation is an organic reaction for the oxidation of primary and secondary alcohols to carboxylic acids and ketones, respectively. It is named after its discoverer, Sir Ewart Jones. The reaction was an early method for the oxidation of alcohols. Its use has subsided because milder, more selective reagents have been developed, e.g. Collins reagent.
Di-tert-butyl-iminodicarboxylate is an organic compound that can be described with the formula [(CH3)3COC(O)]2NH. It is a white solid that is soluble in organic solvents. The compound is used as a reagent for the preparation of primary amines from alkyl halides. It was popularized as an alternative to the Gabriel synthesis for the same conversion. Amines can also be prepared from alcohols by dehydration using the Mitsunobu reaction.
Tris(trimethylsilyl)phosphine is the organophosphorus compound with the formula P(SiMe3)3 (Me = methyl). It is a colorless liquid that ignites in air and hydrolyses readily.
2,4,6-Tri-tert-butylphenol (2,4,6-TTBP) is a phenol symmetrically substituted with three tert-butyl groups and thus strongly sterically hindered. 2,4,6-TTBP is a readily oxidizable aromatic compound and a weak acid. It oxidizes to give the deep-blue 2,4,6-tri-tert-butylphenoxy radical. 2,4,6-TTBP is related to 2,6-di-tert-butylphenol, which is widely used as an antioxidant in industrial applications. These compounds are colorless solids.
In the area of organometallic chemistry, a bulky cyclopentadienyl ligand is jargon for a ligand of the type C
5H
5−nR−
n where R is a branched alkyl and n = 3 or 4. Representative examples are the tetraisopropyl derivative C
5HiPr−
4 and the tris(tert-butyl) derivative 1,2,4-C
5H
2tBu−
3. These ligands are so large that their complexes behave differently from the pentamethylcyclopentadienyl analogues. Because they cannot closely approach the metal, these bulky ligands stabilize high spin complexes, such as (C5H2tBu3)2Fe2I2. These large ligands stabilize highly unsaturated derivatives such as (C5H2tBu3)2Fe2N2.
Di-tert-butylcyclopentadiene is an organic compound with the formula (Me3C)2C5H4, where Me = methyl. It is a colorless liquid that is soluble in organic solvents. The compound is the conjugate acid of the di-tert-butylcyclopentadienyl ligand, (Me3C)2C5H3−}} (sometimes abbreviated Cp‡−). Two regioisomers of di-tert-butylcyclopentadiene exist, depending on the relative location of the double bonds.
2,4,6-Tri-tert-butylpyrimidine is the organic compound with the formula HC(ButC)2N2CtBu where tBu = (CH3)3C. It is a substituted derivative of the heterocycle pyrimidine. Known also as TTBP, this compound is of interest as a base that is sufficiently bulky to not bind boron trifluoride but still able to bind protons. It is less expensive that the related bulky derivatives of pyridine such as 2,6-di-tert-butylpyridine, 2,4,6-tri-tert-butylpyridine, and 2,6-di-tert-butyl-4-methylpyridine.
