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The Di‐π‐methane Photorearrangement of 2,3‐Disubstituted Benzobarrelenes and Benzonorbornadiene − Substituent Effects in Regioselectivity
Author(s) -
Altundas Ramazan,
Dastan Arif,
Ünaldi Nermin S.,
Güven Kutalmis,
Uzun Orhan,
Balci Metin
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(20022)2002:3<526::aid-ejoc526>3.0.co;2-n
Subject(s) - chemistry , regioselectivity , cyclopropane , substituent , cycloaddition , intramolecular force , photoisomerization , medicinal chemistry , ring (chemistry) , dimer , methane , photochemistry , polar effect , isomerization , stereochemistry , organic chemistry , catalysis
2,3‐Disubstituted benzobarrelene and benzonorbornadiene derivatives 16 , 17 , and 18 , containing electron‐withdrawing and electron‐donating substituents, have been synthesized and subjected to triplet‐sensitized photoisomerization. Methyl 3‐methyl‐2‐benzobarrelenecarboxylate ( 16 ) gave two di‐π‐methane rearrangement products. However, methyl 3‐cyano‐2‐benzobarrelenecarboxylate ( 17 ) underwent an intramolecular [2 π + 2 π ] cycloaddition reaction, whilst methyl 3‐cyano‐2‐benzonorbornadienecarboxylate ( 18 ) formed dimer 40 . The formation of these products is discussed in terms of the radical stabilizing effect of the substituents and the destabilizing effect on the formation of cyclopropane ring.