Synthese enantiomerenreiner Heterosteroide durch intramolekulare Hetero‐Diels‐Alder‐Reaktion

Tietze, Lutz F.; Beifuß, Uwe; Lökös, Magdolna; Rischer, Matthias; Göhrt, Axel; Sheldrick, George M.

doi:10.1002/ange.19901020511

Cited by 19 publications

(3 citation statements)

References 28 publications

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“…Reaction of the e.g. pyrazolone 103 with the enantiopure aldehyde 168 obtained from the Hajos−Wiechert ketone, gives the tetracyclic steroid analogue 169 …”

Section: B Synthesis Of Natural Products and Their Analogues By Domin...mentioning

confidence: 99%

“…pyrazolone 103 with the enantiopure aldehyde 168 obtained from the Hajos-Wiechert ketone, gives the tetracyclic steroid analogue 169. 284 A somewhat different reaction takes place if one uses the aldehyde 170, obtained from estrone methyl ether in a few steps, containing a monosubstituted dienophile moiety (Scheme 45). Presumably mainly due to a change of the coefficients at the double bond a bridged compound is obtained instead of an annulated system.…”

Section: B Synthesis Of Natural Products and Their Analogues By Domin...mentioning

confidence: 99%

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Domino Reactions in Organic Synthesis

1996

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“…Reaction of the e.g. pyrazolone 103 with the enantiopure aldehyde 168 obtained from the Hajos−Wiechert ketone, gives the tetracyclic steroid analogue 169 …”

Section: B Synthesis Of Natural Products and Their Analogues By Domin...mentioning

confidence: 99%

Section: B Synthesis Of Natural Products and Their Analogues By Domin...mentioning

confidence: 99%

Domino Reactions in Organic Synthesis

1996

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“…Again, a multitude of analogues can be prepared by variation of the 1,3-dicarbonyl compound and the dienophile moiety in 60 (Scheme 17). 16 D-Homosteroids 17 can be obtained from the D-secoestrone 64 (prepared from 63 18 ) by condensation with Meldrum's acid 2, which leads in the ®rst step of a domino process to a highly reactive 1-oxa-1,3-butadiene 67 followed by an intramolecular hetero-Diels-Alder reaction to give 65 via 66 (Scheme 18). 19 In contrast to the examples described before, a bridged cycloadduct 65 is produced.…”

Section: S Y N T H E S I S O F H E T E R O S T E R O I D S a N D D -Hmentioning

confidence: 99%

Multicomponent domino reactions for the synthesis of biologically active natural products and drugs

Tietze¹,

Modi

2000

Med. Res. Rev.

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Catalytic Asymmetric Friedel–Crafts Alkylation ofβ,γ-Unsaturatedα-Ketoesters: Enantioselective Addition of Aromatic C−H Bonds to Alkenes

et al. 2001

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Aromatic compounds are very important molecules in chemistry and the addition of these compounds to alkenes in the Friedel ± Crafts alkylation constitutes one of the fundamental reactions in synthetic chemistry. [1] The catalytic enantioselective addition of aromatic CÀH bonds to alkenes leading to formation of a new C À C bond is of considerable interest and remains a long-term challenge for chemists. Such a reaction would provide a simple and attractive method for the formation of optically active arylsubstituted compounds from easily available starting materials. Recently, the first examples of catalytic enantioselective addition reactions of aromatic and heteroaromatic compounds to activated carbonyl compounds, [2] a-dicarbonyl compounds, [3] and imines were reported. [4] However, the development of a catalytic enantioselective version of the corresponding Friedel ± Crafts alkylation reaction has, to the best of our knowledge, not been reported, although numerous examples can be given for the non-enantioselective version of this reaction. [1,5] This paper presents the first catalytic highly enantioselective Friedel ± Crafts alkylation, that is, the addition of aromatic C À H bonds to b,g-unsaturated a-ketoesters catalyzed by chiral Lewis acids [Eq. (1)].The reaction of indole (1 a) with methyl 4-phenyl-2-oxo-3butenoate (2 a) can be catalyzed by various metal complexes, and the application of the chiral bisoxazoline (BOX) complexes [6,7] [{(S)-tBu-BOX}M] ((S)-4 a ± c; MCu(OTf) 2 , Cu(SbF 6 ) 2 , and Zn(OTf) 2 , respectively) and [{(S)-Ph-BOX}M] ((S)-4 d; M Cu(OTf) 2 ) gives the optically active Friedel ± Crafts alkylation product 3 a. Some representative screening results are presented in Table 1. The Friedel ± Crafts alkylation reactions with (S)-4 a ± c and (S)-4 d proceed with high conversion. For the reaction catalyzed by (S)-4 a, product 3 a is formed with up to 88 % ee in CH 2 Cl 2 (entry 3), while 74 % ee is found in THF (entry 6). In Et 2 O, with 2 mol % of the catalyst, [17] Clusters with the labile Al III , Fe III , and In III ions were resolved by the same method and also show exceedingly high stability towards racemization. [18] M. Ziegler, A. von Zelewsky, Coord. Chem. Rev. 1998, 177, 257. [19] Crystal structure of DDDD-[(Et 4 N) & Ga 4 2 6 ]´x (solvent): Crystal data were collected using a Siemens SMART diffractometer equipped with a CCD area detector [25] , crystal size 0.30 Â 0.20 Â 0.15 mm, T À 125 8C, graphite-monochromated Mo Ka radiation (l 0.71073 ), cubic, space group I23 (No. 197), a 22.572 (1) , V 11500.5(9) 3 , Z 2, m 0.528 cm À1 , F(000) 3706, 1 calcd 1.07 Mg m 3À , 2V max 37.648. Of the 15 524 reflections measured, 1510 were unique (R int 0.087). The structure was solved by direct methods and refined on F 2 using SHELXTL. [26] Data were corrected for Lorentz and polarization effects. A semi-empirical absorption correction was applied using XPREP (ellipsoidal model, R int 0.0486, T max 0.812, T min 0.755). [26] The carbonyl oxygen atom of the ligand is disordered over two positions...

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Synthese enantiomerenreiner Heterosteroide durch intramolekulare Hetero‐Diels‐Alder‐Reaktion

Cited by 19 publications

References 28 publications

Domino Reactions in Organic Synthesis

Domino Reactions in Organic Synthesis

Multicomponent domino reactions for the synthesis of biologically active natural products and drugs

Catalytic Asymmetric Friedel–Crafts Alkylation ofβ,γ-Unsaturatedα-Ketoesters: Enantioselective Addition of Aromatic C−H Bonds to Alkenes

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