Photoinduced Conformational Switch of Enantiopure Azobenzenes Controlled by a Sulfoxide
摘要:
Two series of enantiopure azobenzenes with a p-tolylsulfoxide at the ortho or meta position with respect to the azo group, have been regioselectively synthesized. Both can act as enantiopure molecular switches showing different structural features owing to the presence of the stereogenic sulfur. The photoisomerization process, studied by UV-vis, circular dichroism (CD), NMR, and chiral HPLC evidenced a double role of the sulfoxide. A transfer of chirality from the sulfoxide to the azo system was observed by CD in both cis and trans-isomers of the meta sulfinyl derivatives 3, whereas this perturbation was evident for the ortho sulfinyl series 7 only in the cis isomer. The NMR study evidenced that the s-cis rigid conformation of the bisaromatic sulfoxide was fixing a different orientation of the overall system in each series both in the trans and cis isomers, by forcing a final U-shaped structure in cis-3 and an S-shaped structure in cis-7. Very different values of specific optical rotations were measured in both trans and cis isomers, also reflecting the existence of distinct chiral entities in the photostationary states. The easy and reversible changes occurring between different conformational states could find applications in the photocontrol of several molecular switches.
ONE-POT AND SIMPLE REACTION FOR THE SYNTHESIS OF ALKYL p-TOLUENESULFINATE ESTERS UNDER SOLID-PHASE CONDITIONS
摘要:
A manipulatively one-pot and rapid method for the synthesis of alkyl p-toluenesulfinate esters 1 from p-toluenesulfinic acid, supported thionyl chloride on silica gel and aliphatic alcohols in solid phase conditions is described.
Asymmetric Synthesis of the Tetrahydropyran Ring, C32−C38 Fragment, of Phorboxazoles
作者:Yasmin Brinkmann、M. Carmen Carreño、Antonio Urbano、Françoise Colobert、Guy Solladié
DOI:10.1021/ol048099s
日期:2004.11.1
of phorboxazoles, (2R,4R,6R)-1, is described using a sulfoxide as chiral auxiliary. Key advances include the stereoselective reductions of beta-keto- or beta,gamma-diketosulfoxides, the acid-catalyzed cyclization of enantiopure sulfinyl hydroxy ketone precursors to the tetrahydropyran ring, and the Pummerer reaction on the pendant sulfoxide to create the formyl group.
Axial Chirality Control During Suzuki−Miyaura Cross-Coupling Reactions: The <i>tert</i>-Butylsulfinyl Group as an Efficient Chiral Auxiliary
作者:Françoise Colobert、Victoria Valdivia、Sabine Choppin、Frédéric R. Leroux、Inmaculada Fernández、Eleuterio Álvarez、Noureddine Khiar
DOI:10.1021/ol9020755
日期:2009.11.19
An efficient route to a new family of axially chiral biaryl ligands by a Suzuki−Miyaura cross-coupling reaction between ortho,ortho′-disubstituted aryl iodides bearing in ortho position a tert-butyl or p-tolylsulfinyl group and ortho-substituted phenyl boronic acids or esters is described. The comparison between the t-BuSO and p-TolSO groups as chiral controllers is reported. The modularity of the
Asymmetric Synthesis of Aryl Benzyl Sulfoxides by Vanadium-Catalysed Oxidation: A Combination of Enantioselective Sulfide Oxidation and Kinetic Resolution in Sulfoxide Oxidation
作者:Pádraig Kelly、Simon E. Lawrence、Anita R. Maguire
Chiral sulfur derivatives in the allylation of acyl hydrazones: C2-symmetric bis-sulfinamides as enhanced chiral organic promoters.
作者:Inmaculada Fernández、Ana Alcudia、Beatrice Gori、Victoria Valdivia、Rocío Recio、María Victoria García、Noureddine Khiar
DOI:10.1039/c0ob00078g
日期:——
Monosulfinamides and C2-symmetric bis-sulfinamides are convenient neutral chiral promoters in the allylation of acyl hydrazones, the nature of the spacer and the substituent at the sulfinyl sulfur are key elements for the enantioselectivity of the process.
Enantiomericallypure P-tolyl sulphinyl-N,N-dimethylthioacetamide (1) was prepared starting from (-)-(S)-menthyl toluene-p-sulphinate. Aldol-type condensation of (1) and subsequent removal of the Sulphinyl group open an entry to optically active β-hydroxy thioacetamides in 40–90% e.e.