SYNTHESIS OF THREE-MEMBERED RINGS WITH TWO HETEROATOMS

4 SYNTHESIS OF THREE-MEMBERED RINGS WITH TWO HETEROATOMS 

Although the three-membered rings with two heteroatoms were discovered only after 1950, they are accessible by very simple procedures familiar to the chemists decades before. The most common starting materials, peracids and N-haloamines, were available to the chemist before 1900 preparation, as well as isolation, follows standard procedures. 

Most ground state syntheses of oxaziridines and diaziridines follow the general scheme outlined for (242). Syntheses from starting materials containing a hetero-hetero bond, reported in the older literature, have not been confirmed. 

Gross rate comparisons indicate that these ring closures proceed considerably faster than analogous substitution reactions not leading to three-membered rings (64AG(E)333). 

Ground state syntheses of diazirines involve dehydrogenation of diaziridines, either isolated or generated in situ. 

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Since syntheses of three-membered rings with two heteroatoms almost always proceed under mild conditions with good yields and from simple starting materials, they are useful intermediates in synthesis. The easy formation of N—O and N—N bonds offers synthetic potentialities. Furthermore, the three-membered ring may serve as a protecting group during additional operations of substitution. 

SYNTHESIS OF THREE-MEMBERED RINGS WITH TWO OXYGEN AND/OR SULFUR HETEROATOMS... 

Thioureas in synthesis of heteroeycles, 18, 99 Three-membered rings with two heteroatoms, 2, 83 24, 63... 

The chemistry of seven-membered rings with three heteroatoms 1,2,4 has improved since CHEC(1984) was published. In the first volume, these compounds were included in Chapter 6.08 devoted to seven-membered rings with two or more heteroatoms and only few references on synthesis were reported. In CHEC-II(1996), a single chapter for these compounds mainly covered new synthetic methods, spectroscopy, and reactivity, but still there was a lack of activity reports. 

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