Bases Triethylamine

Upon addition of a base—triethylamine is often used—the sulfonium salt 7 is deprotonated to give a sulfonium ylide 8. The latter decomposes into the carbonyl compound 2 and dimethyl sulfide 9 through /3-elimination via a cyclic transition state. 

The much stronger base DBU apparently assists in the removal of the hydrogen atom in the 2-position of intermediate 861, which thus seems to be an additional function of the added bases triethylamine or DBU, besides neutralization of the generated HCN. 

If the analyte contains either an acidic or a basic functionality, adjusting the pH of the extraction solvent to make the analyte either ionic or nonionic may be advantageous. To make an analyte that contains an acidic or basic functionality nonionic for extraction into a nonpolar solvent, a small amount (5% or less) of an organic acid (such as acetic acid or trifluoroacetic acid) or organic base (triethylamine) along with methanol (about 10%) can be added to diethyl ether or ethyl acetate. Conversely, buffered solutions can be used to control the pH precisely in such a way as to control the charge on an analyte and thus improve its extraction efficiency into polar solvents. 

It seems reasonable that polyester cyclics could be prepared by an extension of the /wendo-high-dilution [17] chemistry used for the preparation of cyclic carbonate oligomers [18, 19] however, such proved not to be the case. Brunelle et al. showed that the reaction of terephthaloyl chloride (TPC) with diols such as 1,4-butanediol did not occur quickly enough to prevent concentration of acid chlorides from building up during condensation [14]. Even slow addition of equimolar amounts of TPC and butanediol to an amine base (triethylamine, pyridine or dimethylaminopyridine) under anhydrous conditions did not form cyclic oligomers. (The products were identified by comparison to authentic materials isolated from commercial PBT by the method of Wick and Zeitler [9].)... 

The reaction of m-3,4-di- /t-butylthiolone-3,4-diol 74 with thionyl chloride and base (triethylamine or pyridine) produced two diastereomeric cyclic sulfites 3a and 3b. The ratio of 3a to 3b is dependent on the solvent used (Table 3). These teactions are generally high yielding with a greater tendency for the formation of diastereomer 3a (Equation 25) <2003HAC587>. 

Another method of seeking evidence of the EIcBirr mechanism is to exam heavy-atom isotope effects in the leaving group. Of course, these should be much more significant in an E2 process because the bond is breaking in the transition state. For example, Thibblin and co-workersfound that in the base-induced elimination of an alkyl halide in which the p-carbon is unusually acidic (indene derivative, 12), moderately strong bases (triethylamine and methoxide) lead to a significant Cl/ Cl isotope effect = 1.010 1.009, where a maximum effect of... 

It is known" that the 1,2-hydrogen shift reaction is catalyzed by base (triethylamine, alcohols, water). Indeed, the decay of the ylidic adducts of... 

An alternate approach to the palladium catalyzed ethynylation of thiophene derivatives has been reported by Zeni and co-workers. They coupled 2-(butyltelluro)thiophenes with different acetylenes (6.48.), The reaction, which was effectively catalyzed by palladium dichloride, was run in the absence of copper salts. The choice of base (triethylamine) and solvent (methanol) were both crucial for the success of the coupling.70... 

Fluoropyridinium salts with either tetrafluoroborate, hexafluoroantimonate, or hexafluoro-phosphate as a counteranion can be treated with excess base (triethylamine, pyridine, diethyl-amine) at room temperature to give 2-fluoropyridine (bp 125 126°C, d4° 1.131, np° 1.468) in good yield.43 This method has been successfully applied to the preparation of 2-fluoropyridine derivatives 4 possessing electron-donating or -withdrawing substituents using substituted 1-fluoropyridinium tetrafluoroborates.43... 

Protection of primary amines. Primary amines form the cyclic adducts 2 ("Stabasc adducts ) on reaction with I and a base (triethylamine for amines with pK 10 II, -butyllithium for less basic amines). The adducts are stable to n- and. KT-BuLi (-25°), LDA, H 0, CH3OH, KF, and NaHCOj but unstable to HOAc, HC1, KOH, and NaBH. ... 

The Staudinger reaction has been extensively studied for the synthesis of monocyclic p-lactams (Scheme 4, e.g., 19 and 20) [37]. An imine 18, a tertiary base (triethylamine), and acid chloride 17 (or equivalent) are required for this reaction. 

The two substituents on the /3-lactam can be longer and either saturated or unsaturated alkyl groups. The bromo alcohol 259 undergoes cyclization in the presence of base (triethylamine was found to give the best result) to yield the cyclic ether 260 <2005PAC2061>. The unsaturated diiodide 261 yields 262 upon reaction with sodium sulfide <1995TL7913>. 

In 1993, Tripp and Hair83 described a method to promote the direct reaction of the chlorosilyl headgroup with the surface hydroxyls groups, using a nitrogen-containing base (triethylamine). In this method, polymerization is avoided because the base and chlorosilane are not added simultaneously but subsequentially in a two-step process. 

Najera reported that silver perchlorate forms a catalytically active complex with (5)-BINAP (87).55 This complex efficiently catalyzes the reaction of aryl iminoesters 108 with /V-methylmaleimide 114 in the presence of the external base triethylamine (Scheme 2.30, Table 2.8). High enantioselectivity is obtained in this reaction. As a consequence of the low solubility of the silver BINAP complex in the reaction medium toluene, it can be quantitatively recovered from the reaction mixture by simple filtration. The recovered catalyst could be recycled at least 4 times with no apparent loss in activity. Carretero reported that /V-phenylmaleimide also reacted with... 

In the preparation of dynamic nitroaldol systems, different aldehydes and nitroalkanes were first evaluated for reversible nitroaldol reactions in the presence of base to avoid any side- or competitive reactions, and to investigate the rate of the reactions. 1H-NMR spectroscopy was used to follow the reactions by comparison of the ratios of aldehyde and the nitroalcohols. Among various bases, triethylamine was chosen as catalyst because its reactions provided the fastest exchange reaction and proved compatible with the enzymatic reactions. Then, five benzaldehydes 18A-E and 2-nitropropane 19 (Scheme 9) were chosen to study dynamic nitroaldol system (CDS-2) generation, because of their similar individual reactivity and product stabilities in the nitroaldol reaction. Ten nitroaldol adducts ( )-20A-E were generated under basic conditions under thermodynamic control, showing... 

Coupling of a benzoic acid derivative under basic conditions is achieved with alkyl iodides," alkyl chlorides,dimethyl sulfate, or (l,1-dihydroperfluoroalkyl)phenyliodonium triflates. Common bases used arc potassium carbonate or sodium hydroxide (with phase-transfer catalyst). " Again, employing acid chlorides " - or anhydrides, " is the method of choice. The reaction can be performed without further activation, " " but in most cases the transformation takes place in the presence of the usual bases, triethylamine - " or pyridine " " " " " [in some cases 4-(dimethylamino)pyridine is added " ]. In a similar manner carbamates. thiocarbamates, " or thiocarbonates are synthesized. Perfluoropropcn-2-ol... 

Similar results have been obtained with 4,5-dimethoxycarbonyl- and 4-phenyl-l,2,3-triazolides, which displace chlorine from ethyl chloroacetate or /3 -chloropropionate to give both 1-N- and 2-lV-alkylated products. The highest 2-N to l-N selectivity was ca. 5 1 with the base triethylamine in DMF. Furthermore, triazolides add to alkynes to give Michael adducts at the 2-position exclusively (73T3285, 73JOC2708). 

Another method of aetivation is known as the Swern oxidation. Under these conditions a reactive dimethylchlorosulfonium chloride is formed from the reaction of dimethyl sulfoxide and oxalyl chloride (Scheme 2.28b). This then reacts with an alcohol to give an alkoxysulfonium salt. In the presence of a base (triethylamine) this salt fragments with the formation of a carbonyl compound (Scheme 2.28c). 

Amides - nitriles. Primary acid amides are dehydrated to nitriles by treatment with titanium tetrachloride and a base (triethylamine, N-mcthylmorpholine) in THF at 0°. Yields range from 65 to 95%. 

Scheme 2. Synthesis of the tris(aminosilyl)methanes 9a-13a (Y = HC) and -silanes 9b-13b (Y = MeSi) R = 4-CH3C6H4 11, 4-CH3OC6H4 12, 2-F-C6H4 13 auxiliary base Triethylamine.

By far the most important type of reaction displayed by halophosphines is nucleophilic substitution. This is pivotal to the preparation of many other three-coordinate compounds containing either solely P—C, P—O, P—N bonds, or mixed combinations. These reactions are often exothermic and frequently carried out at low temperatures. For the synthesis of phosphorus(III) compounds containing a P—O or P—N bond it is often necessary to add a base (triethylamine or pyridine are frequently used) to capture the hydrogen halide eliminated from these condensation reactions. In the case of P—C bond formation, a variety of routes are possible using various carbon-derived nucleophiles. 

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