Benjamín Ortiz

Asymmetric Synthesis of (S)-(−)-Xylopinine. Use of the Sulfinyl Group as an Ipso Director in Aromatic SE

Optically pure (S)-(-)-xylopinine 2 was prepared in three steps in 52% overall yield. Thus, condensation of the carbanion derived from (S)-4 with the (S)-(E)-sulfinylimine 5 gave a 2:1 mixture of tetrahydroisoquinolines 6a and 6b, differing only in configuration at sulfur. N-Desulfinylation of this mixture gave the diastereomeric sulfoxides which, without separation, were converted into (S)-(-)-xylopinine (2) with loss of the sulfinyl moieties under Pictet-Spengler conditions. This unprecedented ipso electrophilic substitution of a sulfinyl group may have synthetic implications beyond that described in this work.

Synthesis of enantiomerically pure 2-amino alcohols from amino acids mediated by sulfoxides

Abstract Enantiomerically pure (R1,S2)- and (S1,S2)-2-amino alcohols can be easily synthesized by stereodivergent reduction of α′-(N-Boc)amino β-keto sulfoxides (easily synthesized from readily available N-Boc amino ester hydrochlorides) with DIBAH (de 82–92%) and DIBAH/ZnBr2 (de 80%), followed by hydrogenolysis of the C–S bond of the resulting hydroxy sulfoxides and final hydrolysis of the N-Boc protecting group.

Asymmetric synthesis of α-acetylenic epoxides

Abstract Chiral α-acetylenic oxiranes were easily synthesized from readily available propargylic esters by a four-step sequence involving the stereoselective reduction of α′-alkynyl β-keto sulfoxides with DIBAH (de 66–78%) and DIBAH/ZnBr2 (de 78–88%), followed by further reduction of the resulting hydroxy sulfoxides into the corresponding sulfenyl derivatives and final epoxy ring closure via sulfonium salt.

Methyl Sulfinates as Electrophiles in Friedel–Crafts Reactions. Synthesis of Aryl Sulfoxides

The Friedel-Crafts reaction of methyl alkyl- and arylsulfinates with aromatic systems, activated by one or more electron-donating substituents (OH, OMe, NHR, NR(2)), provides alkyl aryl and diaryl sulfoxides under mild conditions and in moderate to good yields. The very high regioselectivity usually observed in these sulfinylation reactions is rationalized on the basis of a Wheland intermediate having a trigonal bypyramidal structure in which steric and electronic interactions are significant factors strongly destabilizing the attack to the ortho positions.

Isomerization of Perezone into Isoperezone and Preparation of Dihydroisoperezinone

Abstract The reaction of perezone 1 with 3,4,5,6-tetrahydro-2-pyrimidinethiol 11 promotes a 1,2-carbonyl transposition in the quinoid ring of 1 giving rise to isoperezone 8, which treated with BF3·Et2O produces dihydroisoperezinone 9.

A stereodivergent approach to syn- and anti-β-hydroxy-γ-amino acids. Enantioselective synthesis of N-Boc-statine and N-Boc-3-epistatine mediated by sulfoxides

Abstract Asymmetric syntheses of the syn- and anti-stereoisomers of N-Boc statine, based on the stereodivergent reduction of a single sulfoxide 5, derived from N-Boc- l -leucine, are reported.

Synthesis and Structure of New Heterocyclic Derivatives of Curcumin

New heterocyclic derivatives of curcumin (3) of different ring size were synthesized by reaction of a key intermediate, 1,7-bis(4-acetoxy-3-methoxyphenyl)hepta-3,5-dione (5) with some bi-nucleophilic molecules. These new synthetic derivatives were obtained in good yields and the structure of all compounds was supported by MS, IR, ID and 2D 1 H and 1 3 C NMR spectra and elemental analysis.

A Simple Method to Prepare Alkyl 3,5-Dioxohexanoates

Abstract A simple and efficient method to prepare alkyl 3,5-dioxohexanoates by alcoholysis of isopropylidene (1-hydroxy-3-oxo-butylidene) malonate is described.

A Convenient Synthesis of Methyl- and Isopropyl-Benzyl Ethers Using Silver(II) Oxide as Reagent

Abstract Substituted bromomethyl- and chloromethylbenzenes and bis(bromomethyl) benzenes were directly converted, in high yields, to the corresponding methyl- and isopropyl- benzyl ethers by treatment with silver(II) oxide in methanol or isopropanol.

The structure of β-isopipitzol

Abstract The Lewis acid catalyzed intramolecular cycloaddition of isoperezone ( 5 ) produced a tricyclic compound containing a new skeleton named β-isopipitzol ( 6 ), perezinone ( 7 ) and dihydroisoperezinone ( 8 ).