Three-membered ring compounds

How can one understand the peculiar geometries of the three-membered rings in 27 Two, somewhat different, viewpoints have been proposed by the two groups which 

TABLE 10. Optimized geometries of monosubstituted three-membered rings (H2Si)2Xa 

Reprinted with permission from J. Am. Chem. Soc., 109, 6577 (1987). Copyright (1987) American Chemical Society126. 

TABLE 11. Strain energies and heats of formation for three-membered rings b 

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On treatment of 5-amino-l,2,3,4-thiatriazole with concentrated hydrochloric acid Freund and Schander obtained a hydrochloride of a sulfur-containing substance which was thought to be a three-membered ring compound [cf. Eq. (19)]. The possibility that it might be a dimer with a six-membered ring was, however, left open. 

The one group of cyclic ethers that behaves differently from open-chain ethers contains the three-membered-ring compounds called epox.id.es, or oxiranes,... 

It should be noted that Baylis-Hillman reaction of Garner s aldehyde with methyl acrylate and DABCO results in racemization of the stereocenter of the amino aldehyde [61]. In the case of substrate 56 such racemization is seriously hampered due to the large inversion barrier in three-membered ring compounds [62]. 

Baird MS, Schmidt T (1996) In de Meijere A (ed) Carbocyclic Three-Membered Ring Compounds. Georg Thieme Verlag, Stuttgart, p 114... 

The structures of the three-membered ring compounds obtained in these reactions are of great interest. The pertinent structural parameters are listed in Table VII. The column headed SSi gives the sum of the bond... 

Structural Parameters of Three-Membered Ring Compounds Derived... 

Addition of elemental chalcogens to the double bonds between silicon and phosphorus gives three-membered ring compounds (Scheme 9).59 A 1,2-di-bromodigermene reacts with S8 to give the four-membered ring compound,60 in... 

A few final examples may illustrate the quite general and steadily growing use of these versatile three-membered ring compounds. 

III. PHOTOCHEMICAL REACTIONS OF THREE-MEMBERED RING COMPOUNDS... 

Possible participation of an intermediate, such as a three-membered ring compound (thiazirine), was briefly discussed. 

Of particular interest is the demonstration that a 1,3-dipole or a three-membered ring compound is a first-formed intermediate in the thermal decomposition. Thus, when 4-benzyl-5-tosyliminothiatriazoline was decomposed in the presence of enamines, adducts were obtained as shown in Eq. (23).64,65... 

The reactions between silylene (H2Si ) and the three-membered ring compounds, oxirane, thiirane, and selenirane, which provide possible routes to Si=X (X = O, S, Se) double bonds were studied by ab initio calculations at the MP2 and QCISD correlated levels of theory <2000CJC1496>. Three possible mechanisms have been examined (Scheme 4). Based on the results, the authors have concluded that the silatane route , via the corresponding oxa-, thia-, and selenasilacyclobutanes, is not a likely mechanism for the production of H2Si=X. 

The possibility of the transient formation of 1,2-siloxetane, thietane, and selenetane in the reactions between silylene (H2Si ) and the corresponding three-membered ring compounds (Scheme 4) has been discussed on the basis of calculated enthalpies and energy barriers for the elementary reactions <2000CJC1496>. 

For three-membered ring compounds, Barbarella et al.47 found that there is proportionality between the 33S chemical shift and the atomic charge of the sulphur atom. 

One atom incorporation reactions are discussed in Chapter II subdivided into carbon, nitrogen, and oxygen incorporation. A few of these reactions are discussed in other sections. Because of their special reactivity most of the three-membered ring compounds used for expansion are combined in Chapter III. Reactions with four-membered intermediates are collected in Chapter IV Reactions of the type 1/9 — 1/10 will be found in Chapter V and those of 1/7 —> 1/8 (see Scheme 1/1) in Chapter VII. Bicyclic starting materials will be discussed in... 

This section only covers [2+ l]-cycloaddition reactions performed with carbenes. The synthesis of trifiuoromcthyl-subsliluted three-membered-ring compounds has been achieved by reaction of carbciies with trifiuoronicthyl-subslituled unsaturated systems and by reaction of trifluoro-melhyl-substituled carbenes with alkenes. 

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