Ring enlargement reaction of phenylmethoxycyclopropenone. Regiospecific mass spectrometric carbon monoxide extrusion in phenylmethoxycyclobutenedione

Abstract

NotesControl Oxidations.-An experiment identical with that described for photosensitized oxidation of cholesterol was run except that no photosensitizer was added. From 2.005 g of cholesterol 1.635 g of unaltered cholesterol was recovered, together with 48.4 mg of I, 1.6 mg of Ila, and 1.0 mg of Ilia, all isolated by the same means previously described. Chromatographic examination of mother liquors following recovery of I, lia, and Ilia indicated that traces of IV, V, 3|3-hydroxycholest-5-en-7-one, cholesta-3,5dien-7-one, cholest-5-ene-3/3,7a-diol, and cholest-5-ene-3/3,70-diol were present, all at much less than 1% levels. A control oxidation including photosensitizer but carried out completely in the dark gave a quantitative recovery of unaltered cholesterol.Control oxidations carried out in cyclohexane instead of in pyridine were run similarly. A cyclohexane solution of 1.9835 g of cholesterol was irradiated for 22 hr and then processed as previously described. Crystalline cholesterol free of other demonstrable sterols was obtained in four crops (total 1.8035 g) and mother liquors after preparative thin layer chromatography gave 23.5 mg of amorphous sterols which contained IV and V in approximately 1:1 proportions but which did not contain any demonstrable Ila or Ilia.

Strain‐Driven, Non‐Catalysed Ring Expansion of Silicon Heterocycles

“…Therefore, carbocycles are generally modified by introduction of substituents to enable the desired reaction [37] . These substituents can be for example fused ring systems, [37] ketones [38] or alkali metals [39] . In contrast, silacycles do not rely on the introduction of specific functional groups or substituents due to a greater polarization of the bonds in the ring system and the presence of a Lewis acidic site.…”

New Syntheses and Ring Expansion Reactions of Cyclobutenimines

“…Cyclobutenimmonium structures were also obtained by [2þ2] cycloaddition of ynamines and the related a-chloroenamines to give chlorides 10 [25,26] or by alkylation of squaric acid amides to give products 11 (Scheme 2). [9,27] In another approach, cyclopropenones [28][29][30][31] or their all-carbon analogues, triafulvenes, react with isonitriles to give cyclobutenimines of type 12 and 13, respectively (Scheme 2). [32] Recently, the conversion of 2,2,4,4-tetrachlorocyclobutanimines 14 to cyclobutenimine acetals 15 by the action of alkoxide in a mixed elimination/substitution process was reported (Scheme 3).…”

4-Iminocyclobutenones: Synthesis and Building-Blocks of Aminohydroquinones and Annulated Quinolines

“…Thione derivatives have been prepared as such 9 or as thioacetals 10,11 and there are scattered reports on cyclobutenimines although no general synthesis is available. [12][13][14] The present study fills this gap and opens the door for a comparison of the cyclobutenone chemistry outlined in Scheme 1 with that of the nitrogen congeners.…”