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Intramolecular Iron( II )‐catalyzed Nitrogen Transfer Reactions of Unsaturated Alkoxycarbonyl Azides: A Facile and Stereoselective Route to 4,5‐Disubstituted Oxazolidinones
Author(s) -
Bach Thorsten,
Schlummer Björn,
Harms Klaus
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010618)7:12<2581::aid-chem25810>3.0.co;2-o
Subject(s) - chemistry , intramolecular force , yield (engineering) , solvolysis , stereoselectivity , medicinal chemistry , catalysis , olefin fiber , silylation , nitrogen atom , ring (chemistry) , reactive intermediate , solvent , organic chemistry , hydrolysis , materials science , metallurgy
Intramolecular Fe II ‐catalyzed reactions of various unsaturated alkoxycarbonyl azides are described. The reactions occur in the presence of stoichiometric amounts of trimethyl silyl chloride employing ethanol as the solvent. The corresponding 2‐alkenyloxycarbonyl azides 5, 9, 18, 20, 22 , and 24 gave the products 7 / 8, 10 / 11, 19, 21, 23 , and 25 of an olefin chloroamination in moderate to good yields (47–72 %). The facial diastereoselectivity of the ring closing C−N‐bond forming step is good both in cyclic ( 20, 24 ) and in acyclic substrates ( 5, 18, 22 ) (>90 % ds ). The subsequent chlorine atom transfer occurs selectively in cyclic systems ( 20, 24 ) and in systems ( 9 b, 18 ) which exhibit a conformational bias in the postulated radical intermediate 14 . The lifetime τ of this elusive intermediate was estimated from the loss of stereochemical information in conformationally unrestricted systems ( 9 a, 22 ) and from the data obtained with a radical clock ( 31 → 32 ). 2‐Alkynyloxycarbonyl azides 34 and 36 also yield chloroamination products which are obtained exclusively as the ( Z )‐isomers 35 and 37 (81–99 % yield). The products of the tert ‐butyl‐substituted substrates 38 undergo an immediate rearrangement/solvolysis reaction in the reaction mixture and gave the 5‐alkoxyoxazolidinones 39 (93–99 % yield).