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AZETIDIN-2-ONES AND RELATED AZETIDINE DERIVATIVES

3 AZETIDIN-2-ONES AND RELATED AZETIDINE DERIVATIVES 5.09.3.1 Structure [Pg.247]

Azetidin-2-one (SO) is a hydrolytically sensitive, colourless solid, m.p. 73-74 °C (75LA2195). Other simple azetidin-2-ones are usually low-melting solids or oils (74LA539) icf. Table 3). [Pg.247]

The N—CO distance of 1.38 A in (58) is rather greater than that of a normal amide (ca. 1.32 A) this has been attributed to ring strain and to inhibition of normal amide resonance by interaction with the N-aryl substituent. This inhibition of resonance is more pronounced in the N-tosyl-4-thioxoazetidin-2-one (59), which exhibits very short C=0 and C=S distances as well as the unusually long C—N bonds (80TL4247). NMR investigations [Pg.247]

The most informative feature of the IR spectra of azetidin-2-ones is generally the /3-lactam carbonyl absorption, the frequency of which is affected by substitution and by fusion of the ring (c/. Table 3). Thus, IR spectra of simple monocyclic /3-lactams generally have absorption maxima in the region 1730-1760 cm while the fused 2- and 3-cephem systems (60) and (61) show IR maxima in the regions 1772-1784 and 1782-1792 cm S respectively (b-72MI50900 p. 318). [Pg.248]

The higher frequencies of the /3-lactam carbonyl absorption in fused systems has been attributed to increased inhibition of amide resonance as the /3-lactam ring becomes less planar (b-72mI50900 p. 303). For the 3-cephems (61) there is also the possibility of enamine resonance which could further reduce the ability of the /3-lactam nitrogen to contribute to amide resonance. [Pg.248]

3 Azetidin-2-ones and Related Azetidine Derivatives 2.01.3.1 Introduction [Pg.36]


IR spectra of systems related to /3-lactams show the expected trends in the frequency of the carbonyl absorption, where present. For example, the presence of an exocyclic double bond at C-4 in an azetidin-2-one raises the value of vc=o considerably. Thus the 4-thioxoazetidin-2-one (62 Z=S) and the derived 4-alkylidene systems (62 Z = CR R ) exhibit /3-lactam carbonyl absorptions at 1835 and 1800-1810 cm respectively (80JOC1477, 80JOC1481), while the 4-iminoazetidin-2-ones (63) have vc=o at 1800-1825 cm (81CC41). Additional spectral data for these and similar systems may be found in the references in Table 5. [Pg.248]

Some work published by Barrett and his group, related to that mentioned earlier, describes how 3-methylene-azetidin-2-ones (73) may be formed from l-lithio-oxy-l-lithio-aminoallene derivatives (72) by reaction with aldehydes followed by manipulation as shown in Scheme 6. [Pg.324]


See other pages where AZETIDIN-2-ONES AND RELATED AZETIDINE DERIVATIVES is mentioned: [Pg.237]    [Pg.247]    [Pg.237]    [Pg.247]    [Pg.237]    [Pg.237]    [Pg.247]    [Pg.237]    [Pg.247]    [Pg.237]    [Pg.73]    [Pg.658]    [Pg.22]    [Pg.112]    [Pg.31]    [Pg.33]    [Pg.33]    [Pg.33]    [Pg.52]    [Pg.33]    [Pg.288]    [Pg.32]   


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