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Oxocarbons and Related Compounds, VIII. - Squaric Amide Chlorides: Simple Methods of their Preparation and Cyclization of Specially Substituted Representatives to Annulated Cyclobutenediones
Schmidt, Arthur H.,Plaul, Wolfgang,Aimene, Amokrane,Hotz, Monika,Hoch, Monika
, p. 1021 - 1035 (2007/10/02)
Squaric dichloride (1c) reacts with a great number of secondary amines and with several primary amines to afford the squaric amide chlorides 4d-z.A further simple method for the preparation of 4a-d, aa-ac has been found in the reaction of 1c with an equimolar amount of the trimethylsilylamines 9a-ac.On using a twofold molar amount of 4-(trimethylsilyl)morpholine (9d), dimorpholinocyclobutenedione (11) has been obtained.Reaction of hexamethyldisilazane (12) with 1c affords 3-amino-4-chloro-3-cyclobutene-1,2-dione (14).The squaric amide chlorides 4m, u-w suffer intramolecular cyclization by the action of AlCl3 to give the annulated cyclobutenediones 17a-d.The analogous cyclization of 4z yields 18 which is characterized by an sevenmembered ring condensed with the cyclobutenedione unit.
