Asymmetric synthesis of (–)-exo-brevicomin. Chirality transfer from a chiral (tetrahy-dropyranyloxyallyl)boronate in the condensation with aldehydes

Wuts, Peter G. M.; Bigelow, Sean S.

doi:10.1039/c39840000736

Cited by 22 publications

(5 citation statements)

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“…Selective conversions of the vinylic sulfoximines II and allylic sulfoximines III to the enantio‐ and diastereopure building blocks IV − VIII can be envisaged considering (i) the facile lithiation of vinylic sulfoximines4,13−17 and allylic sulfoximines2,5,11,12,18−24 at C‐α, (ii) the ready nickel‐catalyzed cross‐coupling reaction of vinylic sulfoximines with organometallics,4,15,25,26 (iii) the excellent Michael acceptor properties of vinylic sulfoximines and their (dialkylamino)sulfoxonium salts,27−30 (iv) the facile reduction of sulfoximines,31 (v) the ready S N reaction of allylic sulfoximines with copper organyls,5−7 (vi) the facile elimination of β‐hydroxy (dialkylamino)sulfoxonium salts under formation of epoxides,32,33 and (vii) the ready substitution of allylic sulfoximines 34. Thus, if attainable, sulfoximines II and III would be expected to considerably expand the range of synthetic possibilities available through the use of either enantio‐ and diastereopure homoallylic alcohols of types II and III bearing an alkyloxy group,35−42 a Cl atom,43−45 a (dialkylamino)carbonyloxy group,10e,46−51 or a silyl group52−54 instead of the sulfonimidoyl group, or by utilizing aldol‐type compounds55,56 and vinylic epoxides as starting materials 57. The feasibility of a synthesis of II from I was indicated by the work of Reggelin et al,11,12 who showed that lithium−titanium exchange using ClTi(O i Pr) 3 of lithiated allyl and crotyl sulfoximines bearing a chiral N ‐(silyloxy)alkyl group instead of the N ‐methyl group allowed their γ‐hydroxyalkylation under the highly regio‐ and diastereoselective formation of vinylic hydroxy sulfoximines of type II in medium to good yields 58.…”

Section: Introductionmentioning

confidence: 99%

N-Methylsulfonimidoyl-Substituted (2-Alkenyl)titanium Complexes: Application to the Synthesis of β- and δ-Sulfonimidoyl-Substituted Chiral Homoallylic Alcohols, X-ray Crystal Structure Analysis, and Fluxional Behavior

et al. 2000

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Enantiopure acyclic (E)‐ and (Z)‐configured allylic sulfoximines have been synthesized from N,S‐dimethyl‐S‐phenylsulfoximine and aldehydes by the addition− elimination−isomerization route through the intermediate generation of the corresponding (E)‐configured vinylic sulfoximines. Isomerization of the vinylic sulfoximines with DBU preferentially afforded the corresponding (Z)‐configured allylic sulfoximines, which were subsequently isomerized by DBU to preferentially yield the (E)‐isomers. Titanation of lithiated (E)‐configured allylic sulfoximines with ClTi(OiPr)3 furnished the corresponding bis(2‐alkenyl)diisopropyloxytitanium(IV) complexes, which reacted with aldehydes in the presence of ClTi(OiPr)3 with high regio‐ and diastereoselectivities at the γ‐position to give the corresponding (Z)‐anti‐configured δ‐N‐methylsulfonimidoyl‐substituted homoallylic alcohols in good yields. In the absence of ClTi(OiPr)3 at low temperatures, only one allylic moiety of the bis(alkenyl)diisopropyloxytitanium complex is transferred to the aldehyde. In this way, a cyclic lithiated allylic sulfoximine has been converted with high regio‐ and diastereoselectivity to the corresponding homoallylic alcohols bearing a vinylic sulfonimidoyl group. Titanation of lithiated (E)‐ and (Z)‐configured allylic sulfoximines with ClTi(NEt2)3 afforded the corresponding mono(2‐alkenyl)tris(diethylamino)titanium(IV) complexes, which reacted with aldehydes with moderate to high regioselectivities and high diastereoselectivities preferentially at the α‐position to give the corresponding syn‐configured β‐N‐methylsulfonimidoyl‐substituted homoallylic alcohols along with the (Z)‐anti‐configured δ‐N‐methylsulfonimidoyl‐substituted homoallylic alcohols in good yields. In this way, the cyclic lithiated allylic sulfoximine was converted with high regio‐ and diastereoselectivity to the corresponding isomeric homoallylic alcohols bearing an allylic sulfonimidoyl group. In the case of mono(alkenyl)tris(diethylamino)titanium(IV) complexes, the regioselectivity of their reactions with aldehydes has been found to depend on the size of the substituent at the CC double bond and the aldehyde, as well as on the configuration of the double bond. Reaction of racemic lithiated N‐methyl‐S‐(3,3‐diphenyl‐2‐propenyl)‐S‐phenylsulfoximine with ClTi(OiPr)3 afforded the corresponding bis(alkenyl)diisopropyloxytitanium(IV) complex. X‐ray structure analysis revealed a distorted octahedral cis,cis,cis‐configured bis(2‐alkenyl)diisopropyloxytitanium(IV) complex, in which the allylic moieties are coordinated in a bidentate fashion through C‐α and the N atom to the Ti atom, both having the relative configuration RSSC. In solution, the titanium complex shows fluxional behavior, which is characterized by topomerization of the isopropyloxy groups and allylic moieties. The exchange of the latter occurs with retention of the configuration at C‐α.

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Section: Introductionmentioning

confidence: 99%

N-Methylsulfonimidoyl-Substituted (2-Alkenyl)titanium Complexes: Application to the Synthesis of β- and δ-Sulfonimidoyl-Substituted Chiral Homoallylic Alcohols, X-ray Crystal Structure Analysis, and Fluxional Behavior

et al. 2000

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“…The anomeric carbon is necessarily chiral, its configuration can be controlled, and it provides a structural conduit for transmitting stereochemical information to the prochiral radical center. The nearest analogies that we could find for a THP-based chiral auxiliary for hydroxyalkyl radicals were the chiral γ-alkoxyallylboronates of Wuts and Hoffmann as well as the glycosylated dienes of Lubineau and Stoodley .…”

Section: Resultsmentioning

confidence: 93%

Development of an Effective Chiral Auxiliary for Hydroxyalkyl Radicals

et al. 2002

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The development of an effective chiral auxiliary for hydroxyalkyl radicals is delineated. Both the 2-tetrahydropyranyl (THP) and tri-O-benzyl-2-deoxy-alpha-D-glucopyranosyl (GLU) auxiliaries resulted in diastereoselective radical additions to methyl acrylate at -78 degrees C (ds = 6/1 and 11/1, respectively). The developing stereochemistry at the radical center was completely under auxiliary control. Correlation experiments showed that the D-GLU auxiliary led to attack on the radical Si-face. The selectivity of these radical additions dropped-off considerably when the more reactive 2-nitropropene trap was employed. Computational studies suggested that the observed facial selectivity was due primarily to entropic factors in the transition state but that a smaller temperature-dependent enthalpic contribution was also involved. It was hypothesized that incorporation of a quaternary center at C-6 (THP numbering) would restore the facial selectivity with more reactive radical traps by restricting the orientations available to the incoming alkene. In the event, the trans-6-tert-butyltetrahydropyranyl (tBu-THP) auxiliary resulted in very good diastereoselection with 2-nitropropene (ds = 35/1 at -78 degrees C, 15/1 at 0 degrees C, and 8/1 at RT) as did the tri-O-benzyl-6,6-dimethyl-2-alpha-D-deoxyglucopyranosyl (diMe-GLU) auxiliary during additions to ethyl alpha-trifluoroacetoxyacrylate (ds = 10/1 at 0 degrees C). A protocol for recovery of the sugar-derived chiral auxiliaries was also established. This work sets the stage for the development of a novel approach to 1, 3, 5.(2n + 1) polyols based on iterative radical homologation as well as the application of these pyranosidic auxiliaries to other synthetically important reactions.

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“…Adduct 23 is an intermediate in the synthesis of spirastrellolide A (Scheme 3). [51] The assumed transition states of these catalytic asymmetric allylation reactions are shown in Scheme 8. [44,45] The reaction of dodecanal with compound 22 in the presence of 2 mol % Zn(OH) 2 and 2.4 mol % ligand 9 proceeded smoothly to afford the corresponding chloroallylated adduct 24, which is the intermediate, in high yield with high diastereo-and enantioselectivities.…”

Section: Asymmetric Reactionsmentioning

confidence: 99%

“…It is noteworthy that the products are useful chiral synthons. [51] The assumed transition states of these catalytic asymmetric allylation reactions are shown in Scheme 8. We assumed a cyclic transition state of the chiral allylzinc species with an aldehyde, in which the aldehyde is activated by Zn.…”

Section: Asymmetric Reactionsmentioning

confidence: 99%

Allylation Reactions of Aldehydes with Allylboronates in Aqueous Media: Unique Reactivity and Selectivity that are Only Observed in the Presence of Water

Kobayashi

Endo

Yoshino

et al. 2013

Chemistry An Asian Journal

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Zn(OH)2-catalyzed allylation reactions of aldehydes with allylboronates in aqueous media have been developed. In contrast to conventional allylboration reactions of aldehydes in organic solvents, the α-addition products were obtained exclusively. A catalytic cycle in which the allylzinc species was generated through a B-to-Zn exchange process is proposed and kinetic studies were performed. The key intermediate, an allylzinc species, was detected by HRMS (ESI) analysis and by online continuous MS (ESI) analysis. This analysis revealed that, in aqueous media, the allylzinc species competitively reacted with the aldehydes and water. An investigation of the reactivity and selectivity of the allylzinc species by using several typical allylboronates (6a-6d) clarified several important roles of water in this allylation reaction. The allylation reactions of aldehydes with allylboronic acid 2,2-dimethyl-1,3-propanediol esters proceeded smoothly in the presence of catalytic amounts of Zn(OH)2 and achiral ligand 4d in aqueous media to afford the corresponding syn-adducts in high yields with high diastereoselectivities. In all cases, the α-addition products were obtained and a wide substrate scope was tolerated. Furthermore, this reaction was applied to asymmetric catalysis by using chiral ligand 9. Based on the X-ray structure of the Zn-9 complex, several nonsymmetrical chiral ligands were also found to be effective. This reaction was further applied to catalytic asymmetric alkylallylation, chloroallylation, and alkoxyallylation processes and the synthetic utility of these reactions has been demonstrated.

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Asymmetric synthesis of (–)-exo-brevicomin. Chirality transfer from a chiral (tetrahy-dropyranyloxyallyl)boronate in the condensation with aldehydes

Abstract: Chirality transfer from a chiral (y-tetrahydropyranyloxyal1yl)boronate is employed to secure the asymmetry in the synthesis of (-)-exo-brevicomin.

Cited by 22 publications

References 0 publications

N-Methylsulfonimidoyl-Substituted (2-Alkenyl)titanium Complexes: Application to the Synthesis of β- and δ-Sulfonimidoyl-Substituted Chiral Homoallylic Alcohols, X-ray Crystal Structure Analysis, and Fluxional Behavior

N-Methylsulfonimidoyl-Substituted (2-Alkenyl)titanium Complexes: Application to the Synthesis of β- and δ-Sulfonimidoyl-Substituted Chiral Homoallylic Alcohols, X-ray Crystal Structure Analysis, and Fluxional Behavior

Development of an Effective Chiral Auxiliary for Hydroxyalkyl Radicals

Allylation Reactions of Aldehydes with Allylboronates in Aqueous Media: Unique Reactivity and Selectivity that are Only Observed in the Presence of Water

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