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
摘要:
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.
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
摘要:
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.
Direct Perfluoroalkylthiolation of Few Chalcogenols
作者:Quentin Glenadel、Thierry Billard
DOI:10.1002/cjoc.201500913
日期:2016.5
Trifluoromethanesulfenamide reagent can react with alcohols, in basic conditions, or with thiols, in catalytic acid conditions, to afford the corresponding trifluoromethanesulfenates or trifluoromethyldisulfides. The use of higher homologs of this reagent leads to synthesis of the nearly unknown perfluoroalkanesulfenates and perfluoroalkyldisulfides.
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.