ISSN:
0009-2940
Keywords:
[3 + 2] Cycloaddition
;
[3 + 2] Cycloreversion
;
5H-Tetrazoles, 5-alkylidene-1,4-dihydro-
;
Aziridinimines
;
1,2,3-Triazoles, 1,4,4-trialkyl-4,5-dihydro-5-imino-
;
1,2,3,4,6,7,8-Heptaazaspiro[4.4]nona-2,7-dienes
;
Photolysis
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Synthesis and Photolysis of 1,4,4-Trialkyl-4,5-dihydro-5-imino-1H-1,2,3-triazoles. - Regio- and Diastereoselective Formation of (Z)-AziridiniminesThe 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.
Additional Material:
4 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19901231118
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