Chiral acyl anion equivalents: asymmetric synthesis of α-methoxytolualdehyde

Colombo, Lino; Gennari, Cesare; Scolastico, Carlo; Guanti, Giuseppe; Narisano, Enrica

doi:10.1039/c39790000591

Cited by 42 publications

(14 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1) 7 for these two electrophiles (PhCHO and Ph 2 CO) a precoordination of the carbonyl O atom at the lithium center can be assumed. Second, in accordance with other reactions of lithiated sulfoxides 24,[48][49][50] and also with aldol reactions 51,52 the formation of six-membered cyclic transition states as given in Scheme 3 can be assumed. Based on the experimental findings, the diastereoselectivities observed in this work can be explained in the following way: the formation of the S S R C -and R S S C -configured products 3a and 4b suggests that the two reactions proceed via the transition state ts2.…”

Section: About the Diastereoselectivitymentioning

confidence: 77%

Lithiated sulfoxides: α-sulfinyl functionalized carbanions

et al. 2015

View full text Add to dashboard Cite

Reactions of alkyl aryl sulfoxides H-CRR'S(O)Ar with n-BuLi-TMEDA (TMEDA = N,N,N',N'-tetramethylethylenediamine) afforded α-sulfinyl functionalized alkyl aryl lithium compounds of the type [Li2{CRR'S(O)Ar}2(TMEDA)2] (1, R/R' = H/H, Ar = Ph; 2, R/R' = H/H, Ar = p-Tol; 3, R/R' = Me/Me, Ar = Ph; 4, R/R' = H/Ph, Ar = Ph; 5, R/R' = Me/Ph, Ar = Ph). The compounds were characterized by (1)H, (13)C and (7)Li NMR spectroscopy and, except for 5, by single-crystal X-ray diffraction analyses. In crystals of 1, 2, 3 and 4 ·Et2O dinuclear molecules with four-membered Li2O2 rings were found. There are no LiCα contacts, thus, "free" carbanions are the main structural feature. Reactions of 1-6 (6, R/R' = H/Me, Ar = Ph) with benzaldehyde and benzophenone afforded the corresponding sulfoxides of the type ArS(O)CRR'CHPhOH (1a-6a) and ArS(O)CRR'CPh2OH (1b-6b), respectively. The reactions yielding / and / proceeded with high diastereoselectivities. By X-ray diffractometry it has been shown that in the case of and the diastereomers consisting of the two enantiomers SSRC and RSSC were formed.

show abstract

Section: About the Diastereoselectivitymentioning

confidence: 77%

Lithiated sulfoxides: α-sulfinyl functionalized carbanions

et al. 2015

View full text Add to dashboard Cite

show abstract

“…spectrum of the resulting solution showed that the parent (1.0 g) in THF (3 ml), PhCHO (0.55 ml) and Triton B (40% in MeOH; 0.4 ml) were added and the mixture was stirred a t room temperature for 24 h. Acetic acid (55 yl) and water (0.5 ml) were added. (2)l-p-Tolysulphinyl-1-p-tolythio-2-phenylethybne (9) .-Irradiation of a solution of (2) in MeOH and chromatography on silica gel-AgNO, afforded pure (9); 6 (CDC1,)…”

Section: Methodsmentioning

confidence: 99%

“…The isolated product (4a), under the reaction conditions, gave the [Eu(tf~)~]. The resonance of the olefinic proton in (9) sarne reaction mixture: (2) (85%) and (4a) (15y0, relative ratio ca. 65 : 15 : 12 : 8).…”

mentioning

confidence: 99%

Chiral acyl anion and enolonium ion equivalents. Asymmetric synthesis of α-methoxy-aldehydes

Colombo¹,

Gennari²,

Scolastico³

et al. 1981

J. Chem. Soc., Perkin Trans. 1

Self Cite

View full text Add to dashboard Cite

The reaction of the lithium derivative of (+)-(S)-p-tolyl p-tolylthiomethyl sulphoxide [(+)-(S)-(f )] with benzaldehyde and phenylacetaldehyde in tetrahydrofuran at -78 'C gives, after methylation of the hydroxy-group, reduction of the sulphoxide, and hydrolysis of the resulting dithioacetal, the corresponding a-methoxy-aldehydes, (-)-(R)-2-methoxy-2-phenylacetaldehyde and (+) -(R)-2-methoxy-3-phenylpropionaldehyde, enantiomeric excess 70 and 46%, respectively. The reaction of (+)-(S)-(f) with benzaldehyde in tetrahydrofuran at room temperature in the presence of Triton B gives the new optically pure reagent (€)-(+)-(S)-l -p-toiylsulphinyl-1 -ptolylthio-2-phenylethylene [ (+)-(S) -(2)], which is a chiral enolonium equivalent. The addition of sodium methoxide to (+) -( S ) -(2) in methanol gives, after reduction of the sulphoxide and hydrolysis of the resulting dithioacetal, (+) -(S) -2-methoxy-2-phenylacetaldehyde, enantiomeric excess 60%. The unfavourable equilibrium in addition of methoxide to (+)-(S)-(2) means that the latter is not very useful as a chiral enolonium equivalent in reactions of this type.t Non-protected a-hydroxy-aldehydes are known to be quite unstable and rapidly rearrange to a-hydroxy-ketones, dimerize, and polymerize (A. Hassner, R. H. Reuss, and H. W. Pinnick, J. Org. Chem., 1975, 40, 3427 and references therein).$ Recently, two different asymmetric syntheses of a-hydroxyaldehydes with high optical purity have been reported, but these methods were only used to obtain a-hydroxy-aldehydes without a-C-H bonds (E. L.

show abstract

“…It is conceivable that the trio1 9 is an intermediate in this catabolism, but the origin of the N-atom in 8 is currently unknown. A related transformation is known [16] during the biosynthesis of mycophenolic acid in fungi where oxidative cleavage of the central (E)-double bond of a farnesyl moiety occurs via a diol and an c( -hydroxy ketone to give a carboxylic acid.…”

mentioning

confidence: 99%

The Bioconversion of (3RS,E)‐ and (3RS,Z)‐Nerolidol into Oxygenated Products by Streptomyces cinnamonensis. Possible Implications for the Biosynthesis of the Polyether Antibiotic Monensin A??

Holmes

Ashworth

1990

Helvetica Chimica Acta

View full text Add to dashboard Cite

The ability of the manensin-producing organism Strepiomyces cinnamonensis to bioconvert the (E)-and (2)-isomers of nerolidol ( = 3,7,1 l-trimethyldodeca-l,6,10-trien-3-0l) into new oxygenated products has been investigated. When a 3H-labelled racemic form of each sesquiterpene was added to fermentations of S. cinnamonensis, several new 3H-labelled products could be detected. Two products were isolated from bioconversion of (E)-nerolidol, the amide 8 and the diol9 (Scheme 2), whereas four products were isolated from bioconversion of (Z)-nerolidol, the epoxydiol 10, trials 11 and 12, and the tetrahydrofuryl alcohol 13 (Scheme 4 ) . Products 9-13 were obtained as a 1 :1 mixture of diastereoisomers, and 12 was shown to arise by the overall anti addition of two OH groups to the trisubstituted (Z)-double bond of (Z)-nerolidol. Both isomers of nerolidol as well as the acetylene 7 are inhibitors of monensin production in shake cultures of S. cinnamonensis.

show abstract

Chiral acyl anion equivalents: asymmetric synthesis of α-methoxytolualdehyde

Abstract: Condensation of a chiral dithioacetal mono-Soxide anion with benzaldehyde leads to or-methoxytolu-aldehyde with high chemical and optical yield.

Cited by 42 publications

References 0 publications

Lithiated sulfoxides: α-sulfinyl functionalized carbanions

Lithiated sulfoxides: α-sulfinyl functionalized carbanions

Chiral acyl anion and enolonium ion equivalents. Asymmetric synthesis of α-methoxy-aldehydes

The Bioconversion of (3RS,E)‐ and (3RS,Z)‐Nerolidol into Oxygenated Products by Streptomyces cinnamonensis. Possible Implications for the Biosynthesis of the Polyether Antibiotic Monensin A??

Contact Info

Product

Resources

About