M. Carmen Carreño

Enantiopure sulfoxides: recent applications in asymmetric synthesis

Sulfoxides are nowadays recognised as powerful chiral auxiliaries that may participate in a wide range of asymmetric reactions. Their high configurational stability, the existence of several efficient methods allowing the access to both configurations as well as their synthetic versatility are characteristic features offering a tremendous potential to develop new applications. Significant recent advances leading to high asymmetric inductions in carbon-carbon and carbon-oxygen bond forming reactions, and applications of homochiral sulfoxides to atroposelective synthesis and asymmetric catalysis are discussed. New uses of sulfoxides in the design of chiroptical switches are also shown.

Highly chemoselective reduction of N-Boc protected lactams

Abstract N-Boc protected lactams can be reduced chemoselectively in the presence of other groups such as esters, nitriles, carbamates or double bonds by first reducing the amide carbonyl group into the corresponding hemiaminal using lithium triethylborohydride followed by further reduction of the hemiaminal intermediate with triethylsilane/Boron trifluoride etherate. This method preserves the chirality present in the substrate.

Mild and regiospecific nuclear iodination of methoxybenzenes and naphthalenes with N-iodosuccinimide in acetonitrile

Abstract A wide range of methoxy substituted benzenes and naphthalenes were regiospecifically iodinated at para position with N -iodosuccinimide in acetonitrile under mild conditions in excellent yields. Methylanisoles afforded only nuclear iodination products.

Efficient asymmetric synthesis of [7]helicene bisquinones

The efficient one-pot six-step domino process which occurs when (SS)-2-(p-tolylsulfinyl)-1,4-benzoquinone (1) reacts with 3,6-divinyl-1,2,7,8-tetrahydrophenanthrenes 2a-c allowed enantioselective access to [7]helicene bisquinones 3a-c with excellent optical purities (96 to > 99% ee).

Asymmetric synthesis of orsellinic acid type macrolides: The example of lasiodiplodin

Abstract The asymmetric synthesis of both enantiomers of methyl lasiodiplodin is described. The chiral centers were created in the very last steps of the synthesis by asymmetric induction of a chiral sulfoxide group.

Synthesis and asymmetric diels-alder reactions of (S)-2-p-tolylsulfinyl-1,4-benzoquinone

Abstract Optically pure (S)-2- p -tolylsulfinyl-1,4-benzoquinone ( 5 ) is readily obtained by deketalization of the corresponding quinone bisketal 4 , synthesized by Andersens type synthesis on 2-bromo-1,4-dimethoxybenzene ( 1 ) followed by anodic oxidation of the resulting sulfoxide. The Diels-Alder reaction of cyclopentadiene with 5 took place on C 5 -C 6 dienophilic double bond showing high facial selectivity, which can be inverted by using different Lewis acids, and total endo selectivity.

Stereoselective synthesis of heterocyclic cage compounds by domino conjugate additions.

Heterocyclic cage compounds have been stereoselectively synthesized from enantiopure [(S)R]-[(p-tolylsulfinyl)methyl]-p-quinols or their amine analogues and 2-(trimethylsilyloxy)furan in the presence of Bu4NF. The method is particularly valuable not only because of the stereochemical control but also because the reactions occur in an experimentally simple one-pot procedure through a domino sequence of three consecutive conjugate additions. The intermediate 1,4-adducts could be isolated when the reaction was carried out in the presence of BF3 x OEt2.

Catalytic activity of chiral β-hydroxysulfoxides in the enantioselective addition of diethylzinc to benzaldehyde.

Abstract The first examples of the use of readily available β-hydroxysulfoxides 1–8 as chiral catalysts in the enantioselective addition of diethylzinc to benzaldehyde are reported. The increase of the steric hindrance around the chiral ligand OH group improves the e.e. of the obtained 1-phenylpropanol, which is higher with tertiary alcohols (25–45%) than with secondary ones (

Asymmetric synthesis of (R) and (S)-4-hydroxy-2-cyclohexenone and derivatives

The asymmetric syntheses of both enantiomers of 4-hydroxy-2-cyclohexenone and their O-acetyl and O-benzyl derivatives are reported. DIBAL and ZnCl2/DIBAL stereosetective reductions of the keto- sulfoxides resulting in the sulfinylation of 1,4-cyclohexanedione ethylene monoketal are the key steps in these syntheses.

(S,S)-bis-p-Tolylsulfinylmethane and carbonyl compounds : reactivity and asymmetric induction

Abstract (S,S)-bis p-Tolylsulfinylmethane was shown to react with aromatic aldehydes with a high diastereoselectivity. In contrast, ,β-unsaturated aldehydes, giving only the elimination products, are in one step transformed into 4-substituted (E, E)-(S,S)-1, 1-bis (p-tolylsulfinyl)-1,3-butadiene.