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23.17.1.1.1.13.1 Variation 1: Photochemical Transformation of 2-(Cyanoimino)-1-diazoalkanes

DOI: 10.1055/sos-SD-023-00727

Perst, H.Science of Synthesis, (200623821.

The photo-induced conversion of 2-(cyanoimino)-1-diazoalkanes 172 in the presence of methanol affords O-methyl imidoyl esters 175[‌184‌‌186‌] via a Wolff-type rearrangement of an iminocarbene intermediate 173 to a ketenimine 174, which is trapped by the alcohol in a subsequent step (Scheme 48).[‌184‌‌186‌] Experimental details of these reactions are not available, although some characterization of one of the resulting O-methyl-N-cyano­imides (175, R1=NPh2) has been reported.[‌186‌] The reactive ketenimine intermediates 174 may be generated quantitatively by UV irradiation (λ >300nm or λ=280nm)[‌185‌] of the diazoalkane derivatives 172 in dichloromethane (at 196°C)[‌184‌,‌185‌] or in an argon matrix (at 263°C).[‌185‌] The ketenimines 174 have been identified by low-temperature IR spectroscopy [IR (CH2Cl2, 196°C) ν̃C=C=N: 2035cm1 (R1=H), 2020cm1 (R1=Me), 2010cm1 (R1=Ph)],[‌184‌,‌185‌] and some of the derivatives 174 (R1=Me, NPh2) have also been trapped by [2+2] cycloaddition with N-phenylbenzylideneamine.[‌185‌,‌186‌] The resulting 2-iminoazetidines (176A and 176B) are diastereoselectively formed with preference for the sterically favored trans-isomer 176A.[‌185‌,‌186‌]

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