170877-37-9Relevant academic research and scientific papers
Diels-Alder reactions of (E)-2-Phenyl-4-[(S)-2,2-dimethyl-1,3-dioxolan-4-ylmethylen]-5(4H)-oxaz olone with heterogeneous catalysts
Cativiela, Carlos,Fraile, Jose M.,Garcia, Jose I.,Lopez, Ma. Pilar,Mayoral, Jose A.,Pires, Elisabet
, p. 2391 - 2398 (2007/10/03)
Diels-Alder reactions of (E)-2-Phenyl-4-[(S)-2,2-dimethyl-1,3-dioxolan-4-ylmethylen]-5(4H)-oxaz olone with 2,3-dimethylbutadiene, cyclopentadiene, and 2-methyl-1,3-butadiene (isoprene) are catalysed by silica gel and aluminium, titanium, and zinc catalyst supported on silica gel. l conversion and asymmetric induction are obtained with very low percentages of E/Z isomerisation. The best results are obtained with ZnCl2 supported on silica gel, and by carrying out the reaction without a solvent. The stereochemistry of the major cycloadducts has been determined by single crystal X-ray structure determination and AM1 calculations of the corresponding transition structures.
Z -2-phenyl-4-[(S)- 2,2-dimethyl-1,3-dioxolan-4-ylmethylen]-5(4H)-oxazolone as the dienophile in asymmetric Diels-Alder reactions
Bunuel, Elena,Cativiela, Carlos,Diaz-De-Villegas, Maria D.
, p. 8923 - 8934 (2007/10/02)
Diels-Alder reactions of Z-2-phenyl-4-[(S)-2,2-dimethyl-1,3-dioxolan-4-ylmethylen]-5(4H)-oxazolone and several cyclic and open chain dienes are studied. Less-reactive dienes required longer reaction times and led to isomerization of the Z-oxazolone and isolation of products derived from the E-isomer; Lewis acid catalysts were used to shorten the reaction times. In all cases high diastereofacial selectivity is observed and Diels-Alder adducts can be obtained in high optical purity. The stereochemistry of adducts has been elucidated by single crystal X-ray structure determinations, 1H-NMR analysis and mechanistic considerations.
