Azetidine derivative

Scheme 1 H NMR shifts and coupling constants of azetidine derivatives...

There are few examples of formation of simple azetidines from [2 + 2] fragments, although this type of approach is important for certain azetidine derivatives, e.g. azetidin-2-ones (see Section 5.09.3). Nitrogen analogues of the Paterno-Buchi route to oxetanes are rare an example involves the photoaddition of 3-ethoxyisoindolone (37) to the enol ether (38) (75JA7288, 72CC1144). 

S.09.3 AZETIDIN-2-ONES AND RELATED AZETIDINE DERIVATIVES 5.09.3.1 Structure... 

A number of azetidine derivatives related to azetidin-2-ones are known (Table 5 see Section 5.09.3.3.5). For many of these, minimal studies of reactivity have appeared. The information available, however, suggests that their reactivity is fairly predictable. This is Illustrated for a few specific examples Table 5 gives leading references for other systems. 

The methods of preparation of azetidine derivatives with exocyclic unsaturation, other than azetidin-2-ones, are summarized in Table 5. 

Four-membered heterocycles are easily formed via [2-I-2] cycloaddition reac tions [65] These cycloaddmon reactions normally represent multistep processes with dipolar or biradical intermediates The fact that heterocumulenes, like isocyanates, react with electron-deficient C=X systems is well-known [116] Via this route, (1 lactones are formed on addition of ketene derivatives to hexafluoroacetone [117, 118] The presence of a trifluoromethyl group adjacent to the C=N bond in quinoxalines, 1,4-benzoxazin-2-ones, l,2,4-triazm-5-ones, and l,2,4-tnazin-3,5-diones accelerates [2-I-2] photocycloaddition processes with ketenes and allenes [106] to yield the corresponding azetidine derivatives Starting from olefins, fluonnaied oxetanes are formed thermally and photochemically [119, 120] The reaction of 5//-l,2-azaphospholes with fluonnated ketones leads to [2-i-2j cycloadducts [121] (equation 27)... 

Funke has observed an interesting reaction of l-azabicyclo[ 1.1.01-butane derivative (115) with DMAD in which an azetidine derivative (117) is formed, presumably through the intermediate 116 [Eq. (19)]. 

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