Diene-dienophile hydrogen-bonding control of Diels-Alder reactions with dienes bearing a remote stereogenic center. Amplification of the receptor nature of dienes by conformational tuning leading to high diastereofacial discrimination
01 Sep 1991-Journal of the American Chemical Society (American Chemical Society)-Vol. 113, Iss: 20, pp 7630-7640
About: This article is published in Journal of the American Chemical Society.The article was published on 1991-09-01. It has received 34 citations till now. The article focuses on the topics: Diene & Benzoquinone.
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TL;DR: The reaction of specifically protected anhydroalditols with (diacetoxyiodo)benzene or iodosylbenzenes and iodine is a mild and selective procedure for the synthesis of chiral 6,8-dioxabicyclo[3.2.1]heptane ring systems under neutral conditions.
Abstract: The reaction of specifically protected anhydroalditols with (diacetoxyiodo)benzene or iodosylbenzene and iodine is a mild and selective procedure for the synthesis of chiral 6,8-dioxabicyclo[3.2.1]octane and 2,7-dioxabicyclo[2.2.1]heptane ring systems under neutral conditions. This reaction can be considered to be an intramolecular glycosidation that goes through an intramolecular hydrogen abstraction promoted by an alkoxy radical followed by oxidation of the transient C-radical intermediate to an oxycarbenium ion. This methodology is useful not only for the preparation of chiral synthons but also for the selective oxidation of specific carbons of the carbohydrate skeleton, constituting a good procedure for the synthesis of protected uloses.
74 citations
TL;DR: In this paper, a study of the preparation, reactivity, and diastereoselectivity of chiral 1-amino-3-siloxy-1,3-butadienes in the Diels−Alder reaction is presented.
Abstract: Described is a study of the preparation, reactivity, and diastereoselectivity of chiral 1-amino-3-siloxy-1,3-butadienes in the Diels−Alder reaction. These dienes were easily prepared in good yield from the corresponding enantiomerically pure substituted pyrrolidines. All the dienes described underwent cycloadditions readily with several activated dienophiles under mild reaction conditions. An amino siloxy diene containing a C2-symmetric 2,5-diphenylpyrrolidine auxiliary was found to provide high diastereofacial control, even at or above room temperature. Upon hydrolysis of the cycloadducts, 4-substituted and 4,5-disubstituted cyclohexenones were obtained with ee's ranging from 85% to >98%. A simple model based primarily on steric arguments was developed to rationalize and predict the absolute configurations of final products obtained by this sequence. The synthetic utility of the methodology was illustrated through a concise enantioselective synthesis of (−)-α-elemene. The synthesis also served to establi...
66 citations
TL;DR: Control experiments suggest that the Lewis acid serves both to tether the diene and dienophile and to induce an "intramolecular" reaction of the resulting "self-assembled" intermediate.
49 citations
TL;DR: This review describes the additions of allylMagnesium reagents to carbonyl compounds and to imines, focusing on the differences in reactivity between allylmagnesium halides and other Grignard reagents.
Abstract: This review describes the additions of allylmagnesium reagents to carbonyl compounds and to imines, focusing on the differences in reactivity between allylmagnesium halides and other Grignard reage...
45 citations
TL;DR: Diels-Alder reactions of various combinations of maleimides and 1,3-dienes with cationic oxazaborolidines as catalysts have been shown to be highly efficient and enantioselective.
42 citations