Azetidines, 2-cyano

Scheme 36 Asymmetric synthesis of 2-( l-aminoalkyl)azetidines from enantiopure 2-cyano-azetidines...

Enantiopure 2-acylazetidines were prepared in good yields from 2-cyano-azetidines. The ketones produced were then transformed into azetidinic amino alcohols 3 by addition of phenyllithium. The latter compounds were found to be efficient ligands for enantioselective catalysis <02TA2619>. 

The absolute configuration of naturally occurring 5(-)-azetidine-2-carboxylic acid has been established (73CL5), and the DL form has been resolved (69JHC993). ORD and CD curves have been determined for 2-methylazetidine and an octant rule has been proposed for the N-chloro- and N-cyano-2-methylazetidines (74T39). 

Irradiation of methacrylonitrile and 2-alkoxy-3-cyano-4,6-dimethylpyridine mixture causes [2+2]photocycloaddition across the C(2)-C(3) bond of the latter to give the bicyclic azetine 4 (45-55%) via an azacyclooctatetraene intermediate <96CC1349>. The [2+2]cycloaddition of )V-acylaldimines and allyltriisopropylsilane to give 2,4-disubstituted azetidines is catalysed by Lewis acids <95CL789>. 

Enantiopure 3-phenyl-2-cyanoazetidines (S)-238 and (K)-238, which are epimeric at C2, are prepared in high yields from (K)-phenylglycinol. A one-pot sequence, including addition of organohthium or allyhnagne-sium bromide to the cyano group and in situ reduction of the resulting imine with sodium borohydride, allowed for the preparation of 2-(l-aminoalkyl)azetidines, which were then protected as N-Boc derivatives (R,S)-239 and (S,it)-239 [112] (Scheme 36). Complete anti diastereoselectivity (dr more than 95 5 by NMR) was observed in both cases. The same sequence... 

The ORD curves and ECD spectra of a number of chiral methyl-substituted cyclic amines, aziridine, azetidine, pyrrolidine and piperidine, and their A-mcthyl, A-halo and A-cyano derivatives, and of (5 )-l-azabicyclo[3.1.0]hexane [(5 )-115] were measured96. 

Some fused ring azetidines having a palladium atom in a five-membered ring have been prepared from 2-amino-methyl-l-methylazetidines (Equation 41) and cyano-l-substituted azetidines (Equation 42) <2005JOM2306>. 

The photoreactions of azides can in most cases be rationalized in terms of intermediate nitrenes. Irradiation of t-butyl azide (106) in nitrogen matrices at 12 K gave the imine (107), but no evidence was obtained for a nitrene intermediate.Photoelimination of nitrogen from 4-azido-2-pyrolinones provides a new synthetic route in high yield to 3-cyano-2-azetidines, as shown, for example, for the pyrrolinone (108) in Scheme 12. ° Zwitterionic intermediates have been... 

As an substitute for ketenes, keteniminium cations can also react with imines to afford /3-lactams. It has been found that ketoketenes give better yields of cycloadducts than do ketene iminium salts, whereas aldoketene iminium salts prevail in corresponding aldoketenes in respective reactions. In addition, ketenimines bearing an electron-withdrawing group (e.g., tosyl, cyano) on the nitrogen atom can react with imines to furnish azetidin-2-imines. ... 

N(4-hydroxycyclohexyl)-3-mercapto/cyano-4-aryl-azetidine-2-one has been synthesized fromN-(4-hydroxycyclohexyl)-arylaldimine byreacting with ethyl a-mercapto/a-cyanoacetate on basic alumina under microwaves (Scheme 54), wherein not only the reaction time were brought down from hours to minutes in comparison to conventional heating but also yields were improved. 

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