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Phthalimido‐nitren II . cis ‐ und trans ‐2,3‐Dimethyl‐1‐phthalimido‐aziridin. Synthese und Solvolysen
Author(s) -
Hoesch Lienhard,
Dreiding André S.
Publication year - 1975
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19750580714
Subject(s) - chemistry , aziridine , steric effects , diastereomer , phthalimide , stereospecificity , nitrene , stereochemistry , medicinal chemistry , catalysis , organic chemistry , ring (chemistry)
Phthalimido‐nitrene II Teil I, siehe [1]. . cis‐ and trans ‐2,3‐Dimethyl‐1‐phthalimido‐aziridine. Synthesis and Solvolytic Reactions Teilweise vorgetragen in der Versammlung der Schweizerischen Chemischen Gesellschaft in St. Gallen am 4. Oktober 1969 und in vorläufiger Form veröffentlicht [2]. The addition of phthalimido‐nitrene ( 2 ), generated by lead tetraacetate oxidation of N‐amino‐phthalimide ( 1 ), to cis ‐ and trans ‐2‐butene gave stereospecifically cis ‐ 3 and trans ‐2,3‐dimethyl‐1‐phthalimido‐aziridine 4 respectively. Acetolysis converted the cis ‐aziridine 3 slowly and the trans ‐aziridine 4 rapidly, again stereospecifically, to threo ‐ 7 and erythro ‐O‐acetoxy‐3‐phthalimidoamino‐2‐butanol ( 8 ) respectively. The velocity relation of the two acetolyses is considered to be due to a difference in steric release on the way to the transition state of a S N 2‐type reaction. Acid‐catalysis converted 7 to threo ‐ 11 and 8 to erythro ‐3‐(N‐acetyl‐N‐phthalimido‐amino)‐2‐butanol ( 12 ). The equilibria in this acetyl migration between oxygen and nitrogen ( threo ‐pair 7:11 = 65:35; erythro ‐pair 8:12 = 91:9) are rationalized on steric grounds. The hydrolyses of 3 and 4 were equally stereospecific, leading to threo ‐ 9 and erythro ‐3‐phthalimidoamino‐2‐butanol ( 10 ) respectively. These two compounds 9 and 10 were also available by reacting phthalimide ( 23 ) respectively with threo ‐ 17 and erythro ‐3‐hydrazino‐2‐butanol ( 18 ) which in turn were prepared by hydrazinolysis of cis ‐ 13 and trans ‐2,3‐dimethyloxirane ( 14 ) respectively. A N‐phthaloyl to N,N′‐phthaloyl rearrangement (possibly base catalyzed) was observed, which converted 9 and 10 to threo ‐ 19 and erythro ‐(N,N′‐phthaloyl)‐3‐hydrazino‐2‐butanol ( 20 ) respectively. It is of interest that in the compounds discussed above the NMR.‐coupling (in deuteriotrichloromethane) between H‐‐C(2) and HC(3) is larger ( J = 6–9 Hz) in the threo ‐series than in the erythro ‐series ( J = 2–3 Hz). This shows a depopulation of the conformers 21a and 22a with anti ‐periplanar arrangement of the hetero substituents, rationalizable by intramolecular hydrogen bonds in the conformers 21b ⇄ 21c and 22b ⇄ 22c . This is confirmed by the observation that the stereomeric pairs 19/20 and 9/10 show equal coupling between HC(2) and HC(3) ( J = 8/8 and 6.6/7 respectively) when the NMR.‐spectra were measured in hexadeuterio‐dimethylsulfoxide, a solvent which can compete with intramolecular hydrogen bonding. An attempt is made to rationalize why the NMR.‐chemical shifts in deuteriotrichloromethane of HC(2) and HC(3) in the threo ‐series lie at higher fields than those in the erythro ‐series, the exception again being the 19/20 , pair, measured in hexadeuterio‐dimethylsulfoxide.