Triethylamine formation mechanism

The use of IV-chlorosulfonyl lactams for the preparation of 3-oxoperhydro-1,2,6-thiadiazine 1,1-dioxides 57 provides a different example of a [5 -F 1]-reaction. These react with a weak base, such as 4-nitroaniline, in combination with triethylamine. The mechanism proposed (Scheme 23) involves formation of an intermediate (55), which is converted to the nucleophile 56 by the action... 

Oxidative dimerization of various 2-benzyloxy-2-thiazoline-5-ones (222) catalyzed by iodine and triethylamine is another example of the nucleophilic reactivity of the C-4 atom (469) (Scheme 112). Treatment of 212 with pyrrolidinocyclohexene yields the amide (223) (Scheme 113). The mechanism given for the formation of 223 is proposed by analogy with the reactivitx of oxazolones with enamines (4701. 4-Substituted 2-phenylthiazol-5(4Hi-ones react with A -morphoiino-l-cyclohexene in a similar manner (562j. Recently. Barret and Walker have studied the Michael addition products... 

The interaction of acid chlorides (167 X = Cl) with imines in the presence of bases such as triethylamine may involve prior formation of a ketene followed by cycloaddition to the imine, but in many cases it is considered to involve interaction of the imine with the acid chloride to give an immonium ion (168). This is then cyclized by deprotonation under the influence of the base. Clearly, the distinction between these routes is a rather fine one and the mechanism involved in a particular case may well depend on the reactants and the timing of mixing. Particularly important acid chlorides are azidoacetyl chloride and phthalimidoacetyl chloride, which provide access to /3-lactams with a nitrogen substituent in the 3-position as found in the penicillins and cephalosporins. 

The most radiation-stable poly(olefin sulfone) is polyethylene sulfone) and the most radiation-sensitive is poly(cyclohexene sulfone). In the case of poly(3-methyl-l-butene sulfone) there is very much isomerization of the olefin formed by radiolysis and only 58.5% of the olefin formed is 3-methyl-l-butene. The main isomerization product is 2-methyl-2-butene (37.3% of the olefin). Similar isomerization, though to a smaller extent, occurs in poly(l-butene sulfone) where about 10% of 2-butene is formed. The formation of the olefin isomer may occur partly by radiation-induced isomerization of the initial olefin, but studies with added scavengers73 do not support this as the major source of the isomers. The presence of a cation scavenger, triethylamine, eliminates the formation of the isomer of the parent olefin in both cases of poly(l-butene sulfone) and poly(3-methyl-1-butene sulfone)73 indicating that the isomerization of the olefin occurred mainly by a cationic mechanism, as suggested previously72. 

Solvolyses of these cyclic vinyl triflates at 100 in 50% aqueous ethanol, buffered with triethylamine, lead exclusively to the corresponding cyclo-alkanones. Treatment of 176 with buffered CH3COOD gave a mixture of cyclohexanone (85%) and 1-cyclohexenyl acetate (15%). Mass spectral analysis of this cyclohexanone product showed that the amount of deuterium incorporation was identical to that amount observed when cyclohexanone was treated with CH3COOD under the same conditions. This result rules out an addition-elimination mechanism, at least in the case of 174, and since concerted elimination is highly unlikely in small ring systems, it suggests a unimolecular ionization and formation of a vinyl cation intermediate in the solvolysis of cyclic triflates (170). The observed solvent m values, 174 m =. 64 175 m =. 66 and 16 m =. 16, are in accord with a unimolecular solvolysis. 

The mechanism for the Pd-catalyzed Csp2—P bond formation proposed by Xu et al. is virtually the same as Hirao s with a slight variation. Oxidative addition of 2-bromothiophene to Pd(0) results in Pd(II) intermediate 84, which then undergoes a ligand exchange to give intermediate 85 with the aid of triethylamine. Triethylamine here serves as a base to neutralize HBr so that the reaction is driven forward. Finally, reductive elimination of 85 furnishes unsymmetrical alkyl arylphosphinate 83, regenerating Pd(0). 

Another possible mechanism for the racemization of amino acid esters involves the in situ, transient, formation of Schiff s bases by reaction of the amine group of an amino acid ester with an aldehyde. Using this approach, DKR of the methyl esters of proline 5 and pipecolic acid 6 was achieved using lipase A from C. ant-arclica as the enantioselective hydrolytic enzyme and acetaldehyde as the racemiz-ing agent (Scheme 2.4). Interestingly, the acetaldehyde was released in situ from vinyl butanoate, which acted as the acyl donor, in the presence of triethylamine. The use of other reaction additives was also investigated. Yields of up to 97% and up to 97% e.e. were obtained [6]. 

Rauhut and coworkers were the first to obtain rate constants from emission kinetic studies and to verify the dependence of kobsi and kobsi on the concentration of the base catalyst and on hydrogen peroxide, respectively. Schowen and coworkers , using TCPO, H2O2 and DPA, with triethylamine as catalyst, observed an oscillatory behavior in emission experiments and proposed a mechanism involving the formation of two HEIs (involved in parallel chemiluminescent reactions) to explain it. Other authors have also observed a similar oscillating behavior but have explained it as a complex... 

The most widely used method for the dehydration of primary nitroalkanes involves their treatment with phenyl isocyanate and triethylamine, introduced in 1960 by Hoshino and Mukaiyama (7). A probable mechanism for the formation of the nitrile oxide is shown in Scheme 6.4. This method is known to be very effective for the preparation of aliphatic or aromatic nitrile oxides. In some cases, the separation of the byproduct A,A -diphenylurea from the reaction mixture may be troublesome. In order to circumvent this problem, 1,4-phenylene diisocyanate was introduced (82,83). The polymeric urea that is formed as a byproduct is largely insoluble in the reaction mixture and can easily be removed. 

Isophorone can be cleanly oxidized by air to l,5,5-trimethylcyclohexene-3,6-dione in the presence of Mn(salen) and triethylamine (equation 2 1 4).524 The mechanism suggested involves carbanion (160) formation from the reaction of NEt3 with /3-isophorone, followed by the formation of an alkyl peroxide-manganese(III) complex (161) which decomposes to the dienone (162).524,56... 

The (EiCBJjp mechanism is a close cousin of the (E1cB)b mechanism. The difference is that in the former the free anion is not formed but exists as an ion pair with the protonated base as counter-ion. An example of a reaction that goes by this mechanism is the formation of bromoacetylene from cis-l,2-dibro-moethylene and triethylamine (Equation 7.31).77 If the rate of elimination from deuterated 1,2-dibromoethylene is compared to the rate from nondeuterated material, kHlkD x 1. Therefore proton abstraction is not involved in the ratedetermining step. Because added Et3 D X- does not affect the rate and be-... 

Reaction of Jt-excessive heterocycles (e.g. thiophene, indole), enol ethers (e.g. dihydropyran) and enol acetates, and carboxylic acids with chlorosulfonyl isocyanate leads in generally excellent yields to A-chlorosulfonylamides. These intermediates are converted into the corresponding nitriles by heating in DMF, although the yields can be somewhat variable. A recent reinvestigation of the N-chlorosulfonylamide to nitrile conversion revealed that treatment of the amides with one equivalent of triethylamine led to formation of the nitriles in excellent yield. Clearly, the mechanisms of the DMF and the EtsN induced transformations are different. 

Elucidate the overall reaction scheme, suggest a structure for the unstable intermediate, and give mechanisms for the formation of 2 and 3 which are consistent with the further observation that when oxygen was bubbled through the triethylamine/cycloadduct mixture, the yield of 2 decreased from 51 to 7% while that of 3 increased from 28 to 73%. 

---