7060-52-8Relevant academic research and scientific papers
2-(Perfluoroalkyl)ethanols by thermal alkylation of ambidentate lactams with 2-(perfluoroalkyl)-1-iodoalkanes, in the presence of added water. A change in mechanism and stoichiometry of the reaction. Isolation of a water adduct of the lactim ether intermediate
Brace
, p. 6504 - 6516 (2007/10/03)
Thermal alkylation of amides by an alkyl halide gives alcohols and esters, and the intriguing behavior of ambidentate lactams in this reaction with 2-(perfluoroalkyl)-1-iodoethanes and lactam 2 is summarized in Scheme 1.2-(Perfluoroalkyl)ethanols (3) are the principal alkylation product, and there is obtained a range of coproducts in varying amounts. A lactim ether salt (6·HI) is the first reaction intermediate in a sequence of reactions. For δ-valerolactam (8) or ε-caprolactam (11), conversion to 3 falls precipitously and R(F)CH=CH2 (4) becomes a major product. However, when water is introduced, alkylation rate of 2 by iodoalkane 1 increases, the conversion to 3 and 4 decreases, and a new lactim ether salt, 7.HI (the water adduct of 6·HI), is formed. Conversion to 3 is suppressed because coproduct 2 is weakly basic and the equilibrium lies on the side of the basic amine salt (7·HI). The mass spectrum of 2-hydroxy-2-[[(2-(perfluorohexyl)ethyl]oxy]pyrrolidine (7) includes the parent ion and a fragment (m/z = 131) of the intact pyrrolidine ring with an attached hydroxy group. Basic hydrolysis of product mixtures containing 7·HI in a protic solvent gives a high yield of 3 and 2. The higher lactams, 8 or 11, with 1 and water give the lactam salts efficiently; yield of 4 is low and yield of 3, by subsequent reaction with base, is high. With water present, the reaction rates of 8 and 1 are greater than for 2 and 1; water increases both the alkylation step and the water displacement step. Improved homogeneity of reaction mixtures and a specific solvent effect in which water stabilizes the bipolar transition state may be responsible for improved rates and yields.
Thermal alkylation of ambidentate lactams with 2-(perfluoroalkyl)-1-iodoalkanes. The effect of reaction conditions and ring size on the synthesis of 2-(perfluoroalkyl)ethanols and the mechanism of reaction
Brace
, p. 2059 - 2071 (2007/10/02)
The perfluoroalkylated long chain alcohols and their derivatives exhibit strong surface activity in solution and novel surface modification properties as adsorbed layers or films. A new, little known synthesis of 2-(perfluoroalkyl)ethanols (R(F)CH2CH2OH) employs a lactam, e.g., 2-pyrrolidinone (2), with an iodoalkane, e.g., C6F13CH2CH2I (1). Alkylation of 2 by heating with 1 gives C6F13CH2CH2OH (3) in 83% distilled yield, and treating the residual lactim ether salt (6·HI) with K2CO3 gives additional 3, up to 94% yield. Rate of alcohol formation (k(alc)) is unaffected by molar ratio of 2:1, yet rate of 1 reaction (k(iodo)) increases 2.44 times with doubling of 2:1 and side product C6F13CH = CH2 (4) decreases from 4 to 2%. For homologous lactams [(CH2)(n)NHC = O] (n = 3-5), selectivities (mol 3:4) are as follows: 5-membered ring, 18.4; 6-membered ring, 0.73; 7-membered ring, 0.13. Conversions to 3 are as follows: 6-membered ring, 19.4%; and 7-membered ring, 1.75%. A three-stop mechanism is proposed: (1) O-alkylation of the lactam by 1 gives lactim salt I; (2) N-substitution of salt I by another molecule of lactam forms a tetrahedral adduct (II); (3) breakdown of salt II gives 3 and iminolactam salt III. In model experiments, heating of 2 and lactim 6 yields 99% of 3 and iminolactam 5 and 1% of 4. By contrast, 7-membered 14 with 2 gives 45% of 3 and iminolactam 12, besides 4 and -caprolactam 16 (20%). For higher lactams, two competitive reactions can be discerned: (1) the S(N)2 displacement of alcohol by N-attack on salt II and a unimolecular, concerted fragmentation of the lactim, to lactam and alkene.
