Photochemical transformations of small-ring carbonyl compounds. XXVIII. 1,5-Hydrogen transfer in the photochemistry of aroylaziridines

Abstract

The photolysis in pentane of ?ra«i-A-fert-butyl-2-phenyl-3-benzoylaziridine (4) has been found to afford four products. The structures have been assigned as 2,5-diphenyloxazole (5), (/3-zerz-butylamino)-Zran.s-benzalacetophenone (6), ZV-zerz-butylbenzalimine, and benzaldehyde. The course of the overall photoreaction is substantially altered for the cw-aziridine. Irradiation of c/j-Ar-terf-butyl-2-phenyl-3-benzoylaziridine (3) gave diphenyloxazole and ZV-zerz-butylbenzalimine with no detectable quantities of 6. Sensitization and emission studies indicate that the reaction is derived from the -* triplet state. The failure to quench implies that the reaction of the ketone is too rapid for diffusion of the excited state to quencher molecule. A mechanism involving transfer of an electron from nitrogen to the excited triplet state followed by a 1,5-proton transfer accounts for the formation of 6. The 1,5-hydrogen transfer route does not seem to be important in the photolysis of the related a,/3-epoxy ketone system.

Phototransformations of C-Benzoylaziridines. Dipolarophilic Trapping of Photogenerated Azomethine Ylides1

“…The inorganic material was filtered off, and removal of the solvent from the filtrate under vacuum Anal. Calcd for C28H27NO6: C,71.03;H,5.70;N,2.95. Found: C,71.42;H,5.46;N,2.84.…”

“Dial Up and Lock In”: Asymmetric Organo-Brønsted Acid Catalysis Incorporating Stable Isotopes

“…In summary, they utilize one or more of the following: multi-step protocols; strongly basic reaction conditions; and/or formation of hazardous nitrene intermediates that require toxic metal salts that afford, in some cases, [2H]-aziridines in low yields and/or with reduced levels of [2H] incorporation. [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] As outlined in Figure 2, we report an organocatalysis milestone: a one-pot, multicomponent, asymmetric organo-Brønsted-acid-catalyzed aza-Darzens reaction that ''dials up and locks in'' one or more identical or different isotopes into optically active aziridines.…”

Regioselective and Stereospecific Synthesis, Crystal Structure and NMR Assignments of N-[(Z)-1-Oxo-1,3-Diphenylprop-2-en-2-yl]-4-Nitrobenzamide

“…5 Thermal or non-thermal, 6 acids or nucleophilic reagents 7-10 and/or photochemical isomerisations 11,12 of aziridines are valuable intermediates in organic synthesis as they undergo a variety of transformations and are easily available and versatile. [13][14][15] Although a large variety of 1-aroylaziridines are known to be isomerised into oxazolines, [16][17][18][19][20] few examples of the isomerisation of the 2-benzoyl-3-phenylaziridines have been reported (Scheme 1). The molecular changes involved in the isomerisation of the 1-benzyl-2-phenyl-3 benzoylaziridine system are markedly dependent on the initial stereochemistry and reaction conditions.…”

“…The molecular changes involved in the isomerisation of the 1-benzyl-2-phenyl-3 benzoylaziridine system are markedly dependent on the initial stereochemistry and reaction conditions. [13][14][15] Although a large variety of 1-aroylaziridines are known to be isomerised into oxazolines, [16][17][18][19][20] few examples of the isomerisation of the 2-benzoyl-3-phenylaziridines have been reported (Scheme 1). [21][22][23][24] Our interests in C-N bond or C-C bond cleavage of the aziridine ring into oxazoles, 24 thiazoles, 25 oxazolines, [26][27][28] motivated our studies of the isomerisation of cis and trans-1,2-…”