From lactams

The preparation of nylon resins from lactam precursors involves ring opening, which is facihtated by a controlled amount of water in the reaction mixture. The salt complex condenses internally to produce the polyamide (57). The synthesis of nylon-6 [25038-54-4] from S-caprolactam is as follows ... 

At higher water concentrations (at higher pressure) (Fig. 3.24), the reaction is considerably more rapid. The prepolymer obtained is further polymerized in another reactor, which has a working pressure of 1 bar or less. The total reaction time of the prepolymerization can be considerably shortened by processing it in an autoclave.812 28 In a laboratory, PA-6 can be synthesized in several ways from m-aminocaprolic acid, from lactam and [Pg.175]

From lactams 266 and 267 the 18,19-didehydro alkaloid corynantheal (258) and its stereosiomers with pseudo and epiallo configurations have also been prepared in racemic form (154). 

A method to prepare 2a based on the work of a related analog [4] was employed for the first mulh-kilogram campaign. In this approach, 2a was prepared from lactam 5, which is derived from an optically enriched P-hydroxy acid. This method requires introduction of the amino group as an 0-benzylhydroxylamine, which we hoped would sufficiently protect the amino group of 2b during amide formation with triazole 3. 

Imidate-derived dipoles have played a prominent role in the synthesis of the pyrrolizidine alkaloid retronecine (121).119 The imidate salt derived from lactam (118) was found to undergo a smooth desilylation reaction to produce azomethine ylide (119). Trapping of this dipole with methyl acrylate affords... 

Using LiAlH4 is a widespread method to generate piperidine rings from lactams. Mechanistically the tetrahedral intermediate 46 is formed first, and this then collapses to the iminium ion 47. The iminium ion is of course more electrophilic than the carbonyl group. Thus after a hydride transfer to the iminium ion and repetition of the reaction sequence again, the tertiary amine 49 is formed. As a matter of principle parallel to this reduction sequence the ketone in ring B is reduced to form 50. 

A valuable part of the [2,3]-sigmatropic rearrangement of ammonium ylides is the fact that stereochemical information can be transferred. For example, Kaiser and co-workers stereoselectively alkylated the C-6 position of penicillin using the nitrogen ylide 46 derived from lactam 45.28 Quatemization of 45 with allyl bromide followed by ylide generation using sodium hydride effected the [2,3]-rearrangement. This resulted in the exclusive formation of P-lactam 47 in 75% yield. 

SYNTHETIC STUDIES ON BIOLOGICALLY ACTIVE ALKALOIDS STARTING FROM LACTAM-TYPE CHIRAL BUILDING BLOCKS... 

SYNTHETIC STUDIES ON BIOLOGICALLY ACTIVE ALKALOID STARTING FROM LACTAM 68... 

Not surprisingly, amides function well as traps for vinyl iodide or vinyl bromide-generated alkenyllithiums. Reduction of the products from lactams 99 and 101 gives valuable intermediates 100 and 102 for alkaloid synthesis 55 56... 

This neuroleptic drug 223313,314 has been labelled with carbon-14 in the 11-position315 (equation 150) and with C3H3 in the methyl group of the 4-methylpiperazine ring315 (equation 151) by reacting des-methyl clozapine 225 (obtained from lactam 226316) with tritiat-ed methyl iodide. 

Enolate ions from lactams, such as A-methylpyrrolidinone (147) did not react with haloarenes in the dark191, but 147 reacted with PhX (Cl,Br,I) and p-iodoanisole under irradiation to give the substitution product 148 (50-60% yield) (equation 97)192. 

A study of ketene A, O-acetals has shown that such compounds derived from lactam acetals may be used in the preparation of larger heterocyclic systems via reaction with a 1,3-dipolar species, the initial cycloadducts stabilizing their structures by aromatization. Pyrrolo[2,3-i/]-l,2,3-triazole derivatives, however, do not undergo such elimination reactions and stable cycloadducts may be obtained. Thus, the lactam acetals (133) give the ketene A,0-acetals (134), which on reaction with p-nitrophenyl azide yield substituted pyrrolo[2,3-d]-l,2,3-triazole derivatives (135) <86CB359l>. 

Isopropyl derivatives were introduced by Pettitt and Stouffer [287] and later studied by other workers [288]. They are prepared by reaction with 2-bromopropane in the presence of sodium hydride in dimethyl sulphoxide. The reaction scheme and the preparation procedure were given in Chapter 4 (see p. 64). Except for Arg, all amino acids under study provided the expected derivatives. The hydroxyl group of Hypro was, however, not protected. The derivatives were found to be stable for a reasonable period of time and were analysed on 3% of OV-17. The extension of this promising one-step method to all protein amino acids did not fulfill expectations, however [288]. Some amino acids (Gly, Gin, Asp and Asn) did not provide detectable derivatives and the others led to multiple peaks. Moreover, significant amounts of by-products were produced, which may interfere. Arg provided a single peak, the mass spectrum of which was identical with that of Orn both derivatives resulted from lactam formation. Isoprop derivatives of 23 common amino acids were separated on 5% of-Carbowax 20M on silanized Chromosorb G with temperature programming (50-240°C). 

A practical method for the synthesis of gem-2,2-disubstituted tertiary amines from the corresponding lactams (or amides) has been reported. It is based on the reaction of thioiminium ions, easily prepared from lactams and amides with primary alkylcerium reagents.40... 

Enaminones were obtained from lactam acetals by reaction with active methylene compounds610. Heterocyclic / -enaminoesters are synthons in the preparation of condensed systems611. Acylated alkyl aminoisobutyrylmalonates (145) can be converted to 3-oxo-2-pyrrolines (146)612,613. 

Another example of the preparation of lactim ethers from lactams and phosphoryl chloride is the transformation of tetrahydro-/ -carbolin-l-one (19) to l-alkoxy-3,4-dihydro-/3-carboline (20)46,47 (Scheme 3). 

Presumably, the synthesis of lactim ethers from lactams and acylat-ing agents, including phosgene and ethyl chloroformate, proceeds via intermediate imidochlorides5 5 57 (Scheme 4). 

The reaction of lactim ethers with hydrazine and its derivatives proceeds readily. The resulting compounds are highly reactive and can be used in different reactions involving the side chain and the cyclic nitrogen atom.5,54,76> 80-82 For example, the treatment of caprolactam hydrazone (40) with nitrous acid results in pentamethyl-enetetrazole (41),54,80,81 and the use of diiferent lactim ethers gives other tetrazoles.32,35 The synthesis of polymethylenetetrazoles from lactim ethers and HN3,83 and also84 from HN3 and O-acyl lactims (or imidochlorides of lactams), obtained from lactams and sulfochlorides or phosphoryl chloride, may be mentioned. 

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