Syntheses of enantiomeric dihydropyrans through stereocontrolled intramolecular cycloaddition
作者:Lutz-F. Tietze、Gunter v. Kiedrowski
DOI:10.1016/0040-4039(81)80059-7
日期:1981.1
Reaction of the cyclic 1, 3-dicarboxylicacidderivatives (1), (2) and (3) with (R)- or (S)-citronellal (4/5) gives the enantiomeric tricyclic dihydropyrans (10), (11), (12) and (13), probably via a 100% stereocontrolled intramolecular cycloaddition.
Intra- and intermolecular hetero-Diels-Alder reactions. 45. Simple and induced diastereoselectivity in intramolecular hetero-Diels-Alder reactions of 1-oxa-1,3-butadienes. Experimental data and calculations
作者:Lutz F. Tietze、Holger Geissler、Jens Fennen、Thomas Brumby、Siegbert Brand、Gerhard Schulz
DOI:10.1021/jo00080a030
日期:1994.1
The simple and induced diastereoselectivity of the intramolecular hetero-Diels-Alder reaction of the alkylidene 1,3-dicarbonyl compounds 7a-e, obtained in situ by Knoevenagel condensation of the aldehydes 5a-e and dimethylbarbituric acid 6, was investigated experimentally and theoretically. In all examples the selectivity is very high; thus the domino reaction of 5a and 6 gives nearly exclusively the trans-fused tricyclic dihydropyran 8 (trans/cis = 98.8:1.2). In the similar reactions of the chiral aldehydes 5b-e and 6 the trans-cycloadducts 28, 33, 36, and 41 are the main products out of four possible diastereomers. The induced diastereoselectivity for the reaction of 5b and 5e with 6 is >99:1 and for the reaction of 5e and Sd-with 6, 95.2:3.6 and 94.1:4.7, respectively. Semiempirical AM1 calculations have been used to locate the transition structures of the intramolecular hetero-Diels-Alder reaction of 7a. The results were employed to create new parameters for the MM2-type force-field to determine the transition structures of 7b-e. The obtained data were compared with the experimental results of the cycloadditions and showed an excellent agreement.
TIETZE, LUTZ F.;BRAND, SIEGBERT;BRUMBY, THOMAS;FENNEN, JENS, ANGEW. CHEM., 102,(1990) N, C. 675-677