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exo ‐Stereoselectivity in Diels‐Alder Addition of Halogenocyclopropenes to Butadienes and Furans
Author(s) -
Müller Paul,
Bernardinelli Gérald,
Pfyffer Jean,
Rodriguez Domingo,
Schaller JeanPierre
Publication year - 1988
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19880710306
Subject(s) - chemistry , stereoselectivity , adduct , diels–alder reaction , stereochemistry , organic chemistry , catalysis
The stereochemistry of the Diels ‐ Alder reaction of 1,2‐dichloro‐3,3‐difluorocyclopropene ( 5a ) to 1,4‐diphenyl‐1,3‐butadiene ( 6 ) and 1,3‐diphenylisobenzofuran ( 7 ) was unambiguously established by X‐ray structure determination. In all cases known so far, tetrahalogenocyclopropenes add exo to open‐chain dienes and furans. The previously reported exo ‐addition product ( 2a ) of l‐bromo‐2‐chlorocyclopropene ( 5b ) to 7 allows assignments of the stereochemistry of other additions of 5b to furans. exo ‐Addition usually predominates, but in some cases endo ‐ adducts are also formed. This contrasts with reports in the literature that 5b adds preferentially endo to open‐chain dienes.