3- -4- 2-alkene-4-lactam

Copolymerizations between pairs of cyclic esters, acetals, sulfides, siloxanes, alkenes, lactams, lactones, /V-carboxy-a-amino acid anhydrides, imines, and other cyclic monomers... 

Monocyclic /3-lactams undergo thermolysis or photolysis to give alkenes and isocyanates or ketenes and imines depending on the substitution pattern (75S547 p. 586). Apparently, thermolysis favours the former pathway while photolysis favours the latter (68CB2669). 

Other isocyanates undergo [2 + 2] cycloaddition, but only with very electron rich alkenes. Thus phenyl isocyanate gives /3-lactams with ketene acetals and tetramethoxyethylene. With enamines, unstable /3-lactams are formed if the enamine has a /3-H atom, ring opened amides are produced 2 1 adducts are also found. Photochemical addition of cis- and traH5-stilbene to phenyl isocyanate has also been reported (72CC362). 

AT-Unsubstituted azetidin-2-ones are versatile intermediates in the preparation of a variety of novel /3-lactam containing systems. They are usually made either by reductive dechlorosulfonylation of alkene/chlorosulfonyl isocyanate cycloadducts cf. Section 5.09.3.3.2), which... 

M-Acyliminium cyclizations of optically active mono- and di-oxygenated hydroxylactam derivatives have been used in the synthesis of a number of natural products. In case of a five-membered lactam the oxygen function adjacent to the iminium carbon directs attack of the internal nucleophile from the least hindered side, opposite to the substituent. In the examples given the size of the newly formed ring is determined by the electronic bias of the alkene substituent. 

Lactams (azetidin-2-ones) can be employed usefully (12) in this alkene-forming procedure ... 

Abstract The photoinduced reactions of metal carbene complexes, particularly Group 6 Fischer carbenes, are comprehensively presented in this chapter with a complete listing of published examples. A majority of these processes involve CO insertion to produce species that have ketene-like reactivity. Cyclo addition reactions presented include reaction with imines to form /1-lactams, with alkenes to form cyclobutanones, with aldehydes to form /1-lactones, and with azoarenes to form diazetidinones. Photoinduced benzannulation processes are included. Reactions involving nucleophilic attack to form esters, amino acids, peptides, allenes, acylated arenes, and aza-Cope rearrangement products are detailed. A number of photoinduced reactions of carbenes do not involve CO insertion. These include reactions with sulfur ylides and sulfilimines, cyclopropanation, 1,3-dipolar cycloadditions, and acyl migrations. 

Under certain conditions, amides can add directly to alkenes to form N-alkylated amides. 3-Pentenamide was cyclized to 5-methyl-2-pyrrolidinone by treatment with trifluorosulfonic acid. Acylbydrazine derivatives also cyclized in the presence of hypervalent iodine reagents to give lactams. When a carbamate was treated with Bu3SnH, and AIBN, addition to an alkene led to a bicyclic lactam. 

The reaction can be done intramolecularly. N-Benzyl pent-4-ynamide reacted with tetrabutylammonium fluoride to an alkylidene lactam. Similar addition of a tosylamide-alkene, with a palladium catalyst, led to a vinyl Al-tosyl pyrrolidine. Similar cyclization reactions occur with tosylamide-alkynes. ... 

Acyl radicals can be generated and they cyclize in the usual manner. A polyene-cyclization reaction generated four rings, initiating the sequence by treatment of a phenylseleno ester with Bu3SnH/AIBN to form the acyl radical, which added to the first alkene unit. The newly formed carbon radical added to the next alkene, and so on. Acyl radicals generated firom Ts(R)NCOSePh derivatives cyclize to form lactams. ... 

A related cyclization of N-sulfonyl-amino-alkenes and NBS gave the bromo-lactam, " and a dichloro-Af,7/-bisallylamide was converted to a dichloro-lactam with FeCl2. ... 

Like the similar cycloaddition of ketenes to alkenes (15-61), most of these reactions probably take place by the di-ionic mechanism c (p. 1078). P-Lactams have also been prepared in the opposite manner by the addition of enamines to isocyanates ... 

The reactive compound chlorosulfonyl isocyanate (ClSOaNCO, forms P-lactams even with unactivated alkenes, as well as with imines, allenes, conjugated dienes, and cyclopropenes. With microwave irradiation, alkyl isocyanates also... 

Treatment of the 1,2-oxazines 52 with carbon monoxide at 1000 psi in the presence of cobalt carbonyl brings about insertion of carbon monoxide to form the 1,3-oxazepines S3 <96TL2713>. A convenient route to P-lactams fused to oxepines is made available by alkene metathesis. Thus reaction of 4-acetoxyazetidin-2-one with ally alcohol in the presence of zinc acetate, followed by iV-allylation of the nitrogen affords the derivative 54 which cyclises by RCM to form the oxazepinone 55 <96CC2231>. The same communication describes a similar synthesis of 1,3-dioxepines. 

An alternative 2+2 route to 3-lactams is to use ketene-like (23) on alkenes and reduce away the sulphonyl group. 

Ozonolysis of alkene 446 in the presence of acetaldehyde afforded diketone 448 through the intermediacy of 447. Ring expansion through Beckmann rearrangement took place when bis-oxime 449 was mesylated and warmed in aqueous tetrahydrofuran (THF). The bis-lactam so formed gave piperidinediol 450 on reduction with lithium aluminium hydride, and this compound was transformed into ( )-sparteine by treatment with triphenylphosphine, CCI4, and triethylamine (Scheme 105) <20050BC1557>. 

Cycloadditions give rise to four-membered rings. Thermal concerted [2+2] cycloadditions have to be antarafacial on one component and the geometrical and orbital constraints thus imposed ensure that this process is encountered only in special circumstances. Most thermal [2+2] cycloadditions of alkenes take place by a stepwise pathway involving diradical or zwitterionic intermediates [la]. Considerably fewer studies have been performed regarding the application of microwave irradiation in [2+2] cydoadditions than for other kinds of cydoaddition (vide supra). Such reactions have been commonly used to obtain /1-lactam derivatives by cycloaddition of ketenes with imines [18-20,117,118],... 

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