Highly Diastereoselective Diels–Alder Reactions with Enantiopure Sulfinyl‐Substituted 1‐Hydroxymethyldienes

Abstract

Enantiopure hydroxy-2- and -3-sulfinyldienes undergo highly selective Diels-Alder cycloadditions with various dienophiles controlled by the chiral sulfur atom. The related hydroxy-2-sulfonyldienes display complementary pi-facial selectivity.

Stereocontrolled Synthesis of Tetrasubstituted Olefins

“…There are two main ways by which the Diels−Alder reaction can be used to generate tetrasubstituted olefins (Scheme ) . Either the diene can be substituted at the C2 and C3 positions, 22b, or a disubstituted alkyne can be used as the dienophile 118 Tetrasubstituted Olefins from Diels−Alder Reactions …”

Cycloadditions and Cyclizations of Acetylenic, Allenic, and Conjugated Dienyl Sulfones

“…Several enantioselective variations of Diels−Alder reactions of dienyl sulfones have been reported. These were effected by attaching a chiral auxiliary group to an enol ether dienophile, by installing a chiral carbinol substituent at the 1-position of the dienyl sulfone, or by means of a chiral alkylsulfonyl moiety at the 2-position . Two examples based on dienyl sulfones 122 and 125 are provided in Scheme .…”

(2S,RS)-6-Phenyl-1-(p-tolylsulfinyl)hexa-3(E),5(E)-dien-2-ol

“…Sul®nyl dienes have been used as an ideal substrate in Diels±Alder cycloadditions, where the presence of the sul®nyl group provides an extra element of stereocontrol (Carren Ä o, 1995). The introduction of a hydroxyl group, bound next to the sul®nyl, to form the so-called sul®nyldienols, provides a new stereogenic centre which can be coordinated by a suitable dienophile through intermolecular hydrogen bonding in the transition state of Diels±Alder cycloadditions, thus providing a new diastereoselectivity control in the reaction, since the role of intermolecular hydrogen bonding in the regio-and stereochemical outcome of Diels±Alder reactions of dienes with hydroxyl groups has been well recognized (Araya-Maturana et al, 1999;Ferna  ndez de la Pradilla et al, 2005). The crystal structures of sul®nyldienols are unknown, but the X-ray crystal structure of the -hydroxysulfoxide moiety of 2-(p-tolylsul®nyl)cyclohexanol has previously been estab-lished (Garcia Ruano et al, 1996).…”