New acylnitroso compounds for the asymmetric oxyamination of dienes
摘要:
A series of new enantiomerically pure acylnitroso compounds have been prepared and tested as dienophiles for the asymmetric oxyamination of dienes. Very high selectivities were obtained with acylnitroso compounds derived from diphenylmethoxymethyl pyrrolidine 2c, the C-2-symmetric pyrrolidines 2d-e and camphorsultam 2f. (C) 1998 Elsevier Science Ltd. All rights reserved.
Chiral acylnitroso dienophiles 14, which were obtained from L-proline and from D-mandelic acid, reacted with cyclohexa-1,3-diene to give the expected diastereoisomers 15 and 16 (Scheme 2 and Table 1). The d.e. values for these Diels-Alder reactions were moderate; they are related to the molecular stiffness of the dienophiles. The absolute configuration of the major cycloadducts was interpreted in terms
achiral 1-silyloxybutadiene 1a with the chiral acyinitroso dienophile 2a gave cycloadduct 4 in high diastereomeric excess (d.e. > 98 %), a result which is undoubtedly due to the C-2 symmetrical chiral dimethylpyrrolidine inductor. Excellent d.e. was also observed when the (R)-prolinol dienophile 2d was reacted with the chiral diene 1b (d.e. = 96 %), whereas cycloaddition of the (S) enantiomer 2e with 1b gave
A series of new enantiomerically pure acylnitroso compounds have been prepared and tested as dienophiles for the asymmetric oxyamination of dienes. Very high selectivities were obtained with acylnitroso compounds derived from diphenylmethoxymethyl pyrrolidine 2c, the C-2-symmetric pyrrolidines 2d-e and camphorsultam 2f. (C) 1998 Elsevier Science Ltd. All rights reserved.
Asymmetric Diels-Alder cycloadditions with acylnitroso dienophiles obtained from L-proline