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Ring Closure Reactions of Disubstituted 4‐Penten‐1‐oxyl Radicals − Towards a Stereoselective Synthesis of allo ‐Muscarine
Author(s) -
Hartung Jens,
Kneuer Rainer
Publication year - 2000
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/(sici)1099-0690(200005)2000:9<1677::aid-ejoc1677>3.0.co;2-x
Subject(s) - chemistry , radical , stereoselectivity , diastereomer , regioselectivity , thiazole , muscarine , ring (chemistry) , medicinal chemistry , stereochemistry , organic chemistry , catalysis , biochemistry , receptor , muscarinic acetylcholine receptor
The trisubstituted functionalized tetrahydrofurans 10 , 11 , 16 , 18 , and 19 were photochemically prepared from 2,3‐ syn ‐ and 2,3‐ anti ‐configured N ‐(3‐benzoyloxy‐5‐hexen‐2‐oxy)thiazole‐2(3 H )‐thione anti ‐ 6 , pyridinethiones 7 , anti ‐ 8 , and BrCCl 3 . The formation of tetrahydrofurans was achieved by an efficient and highly regioselective alkoxyl radical cyclization (5‐ exo ‐trig). The 2,3‐ anti substituted intermediates 9 and 12 cyclize stereoselectively whereas a 2,3‐ syn ‐configured O ‐radical affords both possible diastereomeric addition products in equal amounts. The cyclized tetrahydrofuryl methyl radicals were trapped with the bromine atom donor BrCCl 3 to afford the bromomethyl‐substituted cyclic ethers 10 , 11 , 18 , and 19 in excellent yields. The utility of this reaction was stressed by conversion of one of the newly prepared tetrahydrofurans in a two‐step synthesis into (+)‐ allo ‐muscarine (+)‐ 20 .