PHOTOCHEMICAL FORMATION OF HETEROMETHYLENE CYCLOPROPANES .19. SYNTHESIS AND PHOTOLYSIS OF 1,4,4-TRIALKYL-4,5-DIHYDRO-5-IMINO-1H-1,2,3-TRIAZOLES - REGIOSELECTIVE AND DIASTEROSELECTIVE FORMATION OF (Z)-AZIRIDINIMINES

被引:18
作者
QUAST, H
REGNAT, D
机构
[1] Institut für Organische Chemie, Universität Würzburg, Würzburg
关键词
1,2,3,4,6,7,8‐Heptaazaspiro[4.4]nona‐2,7‐dienes; 1,2,3‐Triazoles, 1,4,4‐trialkyl‐4,5‐dihydro‐5‐imino‐; 5H‐Tetrazoles, 5‐alkylidene‐1,4‐dihydro‐; Aziridinimines; Photolysis; 3 + 2] Cycloaddition; 3 + 2] Cycloreversion;
D O I
10.1002/cber.19901231118
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Synthesis and Photolysis of 1,4,4‐Trialkyl‐4,5‐dihydro‐5‐imino‐1H‐1,2,3‐triazoles. — Regio‐ and Diastereoselective Formation of (Z)‐Aziridinimines The novel 5‐iminodihydro‐1,2,3‐triazoles 14 are synthesized from the 5‐isopropylidenedihydrotetrazole 11 through a ring transformation involving cycloaddition and cycloreversion of alkyl azides 12. Thus, [3 + 21 cycloaddition of 11 and 12 pro‐ duces high yields of the spiro compounds 13. On thermolysis at 120‐ 130°C, the latter undergo clean [3 + 2] cycloreversion into methyl a i d e (12a) and the iminodihydro‐1,2,3‐triazoles 14, which exist as mixtures of diastereomers, e.g. (E)‐/(Z)‐14a = 955, or as a single stereoisomer (E)‐14c. When toluene solutions of 14 are irradiated (≥ 1 280 mm) at ‐ 60°C, the configuration of the products is under kinetic control. Irradiation of 14a affords a quantitative yield of the aziridinimines (E)‐and (Z)‐15a (11:89) besides molecular nitrogen. In order to allow the distinction between the least‐motion and the non‐least‐motion path of product formation, the photolysis of iminodihydro‐1,2,3‐triazoles is studied which are labelled at N‐1 by a deuterated methyl group (14b) or a neopentyl group (14c). Neither photolysis (λ ≥280 nm) nor heating to 120 to 130°C induces any scrambling of the alkyl groups attached to N‐1 and the exocyclic nitrogen atom of 14b and c. The major product from (E)‐/(Z)‐14b (84%) is formed by the non‐least‐motion path leading diastereoselectively to (Z)‐15 b, while the least‐motion products (E)‐ and (Z)‐17b (16%) exhibit a diastereo‐meric ratio of 3: 1. Very similar results are obtained on photolysis of (E)‐14c, except that the least‐motion product (15%) arises only in a single configuration [(E)‐l7c]. In the non‐least‐motion products (Z)‐15b, c, the geometry of the MeN‐CN???R group, fixed by the ring in 14b, c, is completely retained. Therefore, the (Z) diastereoselectivity is interpreted in terms of a one‐bond cleavage leading to diazenyl‐1,3‐diazaallyl diradicals 22 having lifetimes too short for changes of their configuration which is determined by the structure of the precursor. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
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页码:2195 / 2202
页数:8
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