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Diastereoselective Addition of Radicals to Chiral 1,3‐Dioxin‐4‐ones
Author(s) -
Graalfs Heiner,
Fröhlich Roland,
Wolff Christian,
Mattay Jochen
Publication year - 1999
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(199905)1999:5<1057::aid-ejoc1057>3.0.co;2-a
Subject(s) - chemistry , radical , intramolecular force , selectivity , dioxolane , intermolecular force , side chain , double bond , diastereomer , stereochemistry , medicinal chemistry , radical cyclization , photochemistry , organic chemistry , molecule , catalysis , polymer
Intermolecular addition of radicals to the 1,3‐dioxin‐4‐ones 1a,b and 2a,b with (–)‐menthone incorporated as chiral auxiliary in 2‐position were investigated. Photochemically generated radicals from 1,3‐dioxolane, oxolane, and 2‐propanol were added with high facial selectivity from the more exposed a‐side. Intramolecular addition of 1,3‐dioxolan‐2‐yl radicals to chiral dioxinones proceeded less efficiently and with lower selectivity also from the a‐side. Nevertheless, it was possible to form the new spirocyclic compounds 22 – 27 . The 1,3‐dioxin‐4‐ones 32a,b possessing an unsaturated side chain were attacked by radicals at the terminal double bond. In the case of irradiation of 32b in 1,3‐dioxolane a cyclization followed the intermolecular addition of a 1,3‐dioxolan‐2‐yl radical and the dispiro compound 36 was formed. However, the formation of dispiro compound 40 required two reaction steps starting with irradiation of 32b and bromotrichloromethane. The achiral 1,3‐dioxin‐4‐one 44 possessing an unsaturated side chain at C‐2 was attacked by 1,3‐dioxolan‐2‐yl radicals preferentially at C‐6.