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Molecular switches: Calculations on the stereodivergent hetero Diels‐Alder reaction of chiral 1‐oxa‐1,3‐butadienes with different lewis acids
Author(s) -
Tietze Lutz F.,
Schulz Gerhard
Publication year - 1995
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.1995199511271
Subject(s) - chemistry , moiety , asymmetric induction , lewis acids and bases , trifluoromethanesulfonate , imide , diels–alder reaction , intermolecular force , stereochemistry , trimethylsilyl trifluoromethanesulfonate , enantioselective synthesis , molecule , organic chemistry , catalysis
The stereodivergent facial differentiation of the intermolecular hetero Diels‐Alder reaction of the 1‐oxa‐1,3‐butadiene 1 with 2 in the presence of trimethylsilyl trifluoromethanesulfonate (TMS‐OTf) or Me 2 AlCl is explained on the basis of semiempirical calculations (AM1 and PM3). The oxabutadiene 9 was shown to prefer the anti arrangement of the carbonyl groups of the imide moiety in the ground state by 1.8 kcal/mol (Am1) or 2.2 kcal/mol (PM3). In the silylated compound 10 this preference is even more pronounced. In contrast, in the chelate 11 the imide moiety is fixed in a syn conformation. The orientation of the oxazolidinone rings in 10 and 11 is opposite: thus, the absolute configuration of the cycloadducts is determined by a facial differentiation due to an asymmetric induction under chelate control ( 11 ) or nonchelate control ( 10 ).