Face Selectivity of the  Diels ‐ Alder  Reaction of 5,6‐Bis((D)methylidene)‐2‐bicyclo[2.2.2]octene | Zendy

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Face Selectivity of the Diels ‐ Alder Reaction of 5,6‐Bis((D)methylidene)‐2‐bicyclo[2.2.2]octene

Author(s) -

Avenati Macro,

Vogel Pierre

Publication year - 1983

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.19830660427

Subject(s) - chemistry , dimethyl acetylenedicarboxylate , selectivity , octene , bicyclic molecule , moiety , medicinal chemistry , double bond , tetracyanoethylene , maleic anhydride , cycloaddition , stereochemistry , organic chemistry , ethylene , catalysis , polymer , copolymer

The face selectivity ( endo ‐face vs. exo ‐face attack onto the exocyclic s‐ cis ‐butadiene moiety) of the [4+2]cycloadditions of 5,6‐bis((D)methylidene)‐2‐bicyclo‐[2.2.2]octene ( 11 ) to strong dienophiles has been determined in benzene at 25°. It is ca. 95/5, 75/5, 70/30, 60/40 and 50/50 for N ‐phenyltriazolinedione (NPTAD), tetracyanoethylene (TCE), dimethyl acetylenedicarboxylate (DMAD), maleic anhydride (MA) and singlet oxygen ( 1 O 2 ), respectively. The endo ‐face preference is probably due to a participation of the homoconjugated double bond at C(2), C(3) which makes the etheno bridge more polarizable than the ethano bridge in 11. The absence of face selectivity with 1 O 2 is consistent with an entropy‐controlled mechanism involving the intermediacy of an exciplex.

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