ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Facile synthetic routes to 1,2-dicyanocyclobutene (3), cyclobutene-1,2-dicarboxylic acid (56) and derivatives thereof are presented, starting from 1,2-dicyanocyclobutane (1), a commercially available acrylonitrile cyclodimer.The favored mode of [4+2]-cycloadditions of 3 to cyclic dienes with sp3carbon atoms is the endo-addition (above 90% relative yields of adducts with endo-cyclobutane ring). Exo-cycloaddition, however, is preferred by dienes having no sp3-carbon atom (e.g. furane). Cyclisation reactions involving cis-vicinal substituents in [4+ 2]-cycloadducts afford (m.n. 2)-azapropellanes 18, 74 and 77. 1H- and 13C-NMR. spectra of the stereoisomeric adducts are discussed in detail. The structures of the furane adducts 14 and 15 were determined by 1H-NMR. using the shift reagent Eu(dpm)3.Reactive butadienes 32, 53-55 are obtained in high yield and purity by gasphase thermolysis (380-420°) of the correspondingly substituted cyclobutenes. 2,3-Dicyanobutadiene-l, 3 (32) gives good yields of [4 + 2]-cycloadducts with strained cycloolefines, moderate yields with vinylethers and non-activated olefins, and no adducts at all with electrophilic dienophiles (8.g. maleic anhydride, fumaronitrile). Thus, reactions of 32 are typical Diels-Alder reactions with ‘inverse electron demand’.Some of these primary [4+2]-cycloadducts (38, 39 and 45) were dehydrogenated to new aromatic ortho-dinitriles 46-48.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19730560839
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