Hydrogen chloride lactams

Hydrogen chloride Lactam ring elimination a,j -Etbylene-j -cyanoketones s. 17, 815... 

In the event, iodolactonization of the carboxylate salt derived from the ester 458 afforded 459, and subsequent warming of the iodo lactone 459 with aqueous alkali generated an intermediate epoxy acid salt, which suffered sequential nucleophilic opening of the epoxide moiety followed by relactonization on treatment with methanol and boron trifluoride to deliver the methoxy lactone 460. Saponification of the lactone function in 460 followed by esterification of the resulting carboxylate salt with p-bromophenacylbromide in DMF and subsequent mesylation with methanesulfonyl chloride in pyridine provided 461. The diazoketone 462 was prepared from 461 by careful saponification of the ester moiety using powdered potassium hydroxide in THF followed by reaction with thionyl chloride and then excess diazomethane. Completion of the D ring by cyclization of 462 to the keto lactam 463 occurred spontaneously on treatment of 462 with dry hydrogen chloride. 

The cyclohexanone in Eq. (21.17) exists in the form of oil droplets and forms a heavier lower phase in cyclohexane. This lower phase undergoes a Beckmann rearrangement with excess sulfuric acid or oleum to give caprolactam. Hydrogen chloride is displaced by the stronger acid and recycled to nitrosyl chloride production [see Eq. (21.16)]. The rearrangement reaction mixture is neutralized with ammonia water to give crude lactam and ammonium... 

This undesirable side reaction is avoided in the polymerization of N-substituted lactams i.e., N-alkyl, N-aryl, or N-acyl lactams. Polymerization of N-substituted lactams proceeds differently, thus in the presence of hydrogen chloride the following sequence of reactions takes place [217]. 

The hydrogen chloride gas evolved is absorbed in dilute hydrochloric add, and then sent to the production of nitrosyl chloride. The solution of lactam in sulfuric add is neutralized by ammonia. Two phases are formed the upper layer is the crude caprolactam which is purified1l5 and the bottom layer is an aqueous solution of ammonium sulfate. The molar yield of caprolactam is 81 per cent of theory in relation to cydohexane. Co-production of ammonium sulfate is 1.7 kg/kg of product... 

Conversion of lactam 36 into racemic iV -benzoylmeroquinene and its esters (42) was accomplished by two routes. Opening of the lactam ring with boiling ethanolic hydrogen chloride led to the amino ester 43 (R = CaHe X = NHg) which was transformed by pyrolysis of the corresponding tertiary iV -oxide into racemic iV-benzoylmeroquinene ethyl ester [42 R = C2H5 mp 67-68°]. 

With ethanolic hydrogen chloride, the p-lactam 14 gave the ethyl ester 16 [50]. 

Reaction with barrelene The reaction of CSI with barrelene (1) leads to the expected lactam (2) when heated in DMF, (2) is converted to the yK hloro nitrile (3). This substance undergoes 1,3-elimination of hydrogen chloride when... 

Hydrogen chloride Aminocarboxylic acids from lactams... 

The nitroketone 118 (see Section IV,B,1) was treated with hydrogen chloride in ethanedithiol to afford the thioketal 119. Reduction of 119 with zinc and acetic acid and further treatment with Raney nickel in ethanol furnished lactam 120. Hydrolysis of 120 in aqueous methanol containing K2C03 gave 121, which on LAH reduction horded the amine 122. On treatment with sodium methoxide, the iV-chloro derivative of 122 gave verazine (123) (215). 

The synthesis of trans-3-acyl- 3-lactam methyl esters 107 has been reported by Almqvist and coworkers [81, 82] by the Staudinger reaction of ketenes, generated from the Meldrum s acids 105, with methyl (i )-thiazoline-4-carboxylate 106 in benzene in the presence of hydrogen chloride (Scheme 3.36). An exceptionally low yield of 38% was obtained in the reaction of acetylketene. These esters could then be selectively reduced to the corresponding aldehydes 108 in moderate yields using diisobutylaluminum hydride (DIBAL-H). The Meldrum acids are well-known precursors of ketenes [83, 84]. They undergo a pericyclic reaction under thermal influence to generate ketenes with the release of carbon monoxide and acetone. 

If, however, traces of water are present in the reaction mixture and gaseous hydrogen chloride is the catalyst, the intermediate lactam hydrolyzes partially to a-aminopimelic acid which reacts further to yield dWysine. ... 

A different method was utilized to prepare III (24) in order to avoid all possible doubt, resulting from the utilization of the Cbzo-glutamic anhydride, which reacts to give a mixture of isomers a and 7 (378,435). This method is based on the opening of the lactame bond of the pyrrolidone nucleus by treatment of 2-pyrrolidone-5-carboxylic acid and its amide with hydrogen chloride-saturated ethanol. 

At the end of the 1930s, the cationic polymerization as well has been attempted by Schlack, who discovered that anhydrous hydrogen chloride was capable of initiating the polymerization of CL. However, for reasons unknown at that time, the acid-initiated reartion did not yield high-quality PA6 and was therefore considered to be of no interest for commercial purposes. As a matter of fact, the cationic mechanism of lactam polymerization has always found very limited applications, if any, not only because of the low conversions and the low molar masses of the resultant polyamides but also for the extensive occurring of side reactions. 

Tire reaction mechanisms can be very complex since they are functions of both the initiating system and the lactam substitution. Among the various mechanisms, the polymerization initiated by protic inorganic adds, such as hydrogen chloride or bromide, will be those mainly considered and described in detail in the present section. 

The regenerated hydrogen chloride enters again into the initiation reaction [31]. Besides this main growth reaction, other competitive propagations are present. In fact, the acyl chloride group may react directly with the lactam monomer in this case, the aminoacyl chloride acts as the acceptor and the monomer as the donor [33] ... 

Without other alternatives, the carboxyalkyl radicals couple to form dibasic acids HOOC(CH)2 COOH. In addition, the carboxyalkyl radical can be used for other desired radical reactions, eg, hydrogen abstraction, vinyl monomer polymerization, addition of carbon monoxide, etc. The reactions of this radical with chloride and cyanide ions are used to produce amino acids and lactams employed in the manufacture of polyamides, eg, nylon. 

In a formal synthesis of quinolizidine 233A 296, the 2,6-m-disubstituted piperidine 292, as a mixture of dia-stereomers, was transformed into 293 by N-acylation with but-3-enoyl chloride. An RCM afforded 294, which was transformed into 295 by hydrogenation of the double bonds and hydride reduction of the lactam, thereby completing a formal synthesis <2000JOC8908> of quinolizidine 233A 296 (Scheme 65) <2004JA4100>. 

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