Premium
On the Addition of Lithiated 2‐Alkyl‐ and 2‐(Chloroalkyl)‐4,5‐dihydro‐1,3‐oxazoles to Nitrones − A Mechanistic Investigation
Author(s) -
Capriati Vito,
Degennaro Leonardo,
Florio Saverio,
Luisi Renzo
Publication year - 2002
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200209)2002:17<2961::aid-ejoc2961>3.0.co;2-f
Subject(s) - oxazole , chemistry , nonane , oxalic acid , alkyl , medicinal chemistry , quenching (fluorescence) , nitrone , stereochemistry , organic chemistry , fluorescence , physics , quantum mechanics , cycloaddition , catalysis
The addition of 2‐(lithioalkyl)‐4,5‐dihydro‐1,3‐oxazoles 2a − c and 2‐[chloro(lithio)alkyl]‐4,5‐dihydro‐1,3‐oxazoles 2d , e to nitrones 3 has been studied. While lithiated 2‐methyl‐4,5‐dihydro‐1,3‐oxazole 2a adds stereoselectively to nitrones 3 , resulting after long reaction times (3 h) in the formation of 2‐[( E )‐alkenyl]‐4,5‐dihydro‐1,3‐oxazoles 8a − h , lithiated 2‐(chloromethyl)‐4,5‐dihydro‐1,3‐oxazole 2e affords 2‐[( Z )‐alkenyl]‐4,5‐dihydro‐1,3‐oxazoles 26a − d and 26f − h . α‐Lithiated 2‐ethyl‐4,5‐dihydro‐1,3‐oxazole 2b adds to 3a to give the 1,6‐dioxa‐2,9‐diazaspiro[4.4]nonane 9 and 2‐alkenyl‐4,5‐dihydro‐1,3‐oxazole 14 after treatment with oxalic acid. Quenching after short reaction times shows that the conversions of 2a to 8 and of 2b to 14 go through spirocyclic compounds 7 and 9 , while the reaction between 2e and 3a , quenched even at short reaction times, gives a mixture of the 1,6‐dioxa‐2,9‐diazaspiro[4.4]nonanes 21‐H and 22‐H and the 2‐(1,2‐oxazetidin‐4‐yl)‐4,5‐dihydro‐1,3‐oxazoles 25a and 27a . The addition of 2c to 3a furnishes the 1,6‐dioxa‐2,9‐diazaspiro[4.4]nonane 15 and then isoxazolidin‐5‐one 16 upon hydrolysis with oxalic acid. The addition of 2d to 3a gives the 1,6‐dioxa‐2,9‐diazaspiro[4.4]nonanes 17b and 18b after short reaction times and the 2‐(1,2‐oxazetidin‐4‐yl)‐4,5‐dihydro‐1,3‐oxazole 19 after long reaction times. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)