A Generic and Reproducible Route to Homo- and Heteroannular Bicyclic β-Diketones via Knochel-Type 1,4-Conjugate Additions to α,β-Unsaturated Cycloalkenones

A cheap synthesis of the so‐called ‘decalin‐1,8‐diones’ started with the conjugate (1,4‐) addition of cyclohex‐2‐en‐1‐one derivatives to the γ‐position of the dilithium derivative (buta‐1,3‐diene‐1,1‐bis(olate)) of crotonic acid. Hydrogenation of these ‘1,4‐γ’ adducts and final cyclization afforded the enol tautomers of decalin‐1,8‐diones. Nucleophilic substitutions at these 3‐oxoenols by NH3 or primary amines created only monoamino products (namely, 3‐oxoenamines) whose reactions with OPCl3 yielded dihydro(1,3,2)oxazaphosphinin‐2‐one derivatives. The two regioisomers of a trimethyl‐3‐oxoenamine served as models for the constitutional assignments of the two rapidly interconverting (hence, individually NMR‐invisible), tautomeric trimethyl‐3‐oxoenols. Such methyl substitutions served to break the ‘pretended’ symmetry of ‘decalin‐1,8‐dione’. Hydrazine and 3‐oxoenols furnished oxygen‐free indazole derivatives whose N−H bonds exchanged with t1/2=ca. 0.00035 s at ca. −58(9) °C.

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Short Syntheses of some ‘Decalin‐1,8‐diones’ and their Derivatives: Breaking the Pretended Symmetry

Knorr

Nadolny

Hauer

et al. 2019

Helvetica Chimica Acta

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Access to Functionalized Quaternary Stereocenters via the Copper-Catalyzed Conjugate Addition of Monoorganozinc Bromide Reagents Enabled by N,N-Dimethylacetamide

Fulton

Alley

Rensch³

et al. 2018

J. Org. Chem.

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Monoorganozinc reagents, readily obtained from alkyl bromides, display excellent reactivity with β,β-disubstituted enones and TMSCl in the presence of Cu(I) and Cu(II) salts to synthesize a variety of cyclic functionalized β-quaternary ketones in 38-99% yields and 9:1-20:1 diastereoselectivities. The conjugate addition features a pronounced improvement in DMA using monoorganozinc bromide reagents. A simple one-pot protocol that harnesses in situ generated monoorganozinc reagents delivers comparable product yields.

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Total Synthesis of (−)-Batrachotoxinin A: A Local-Desymmetrization Approach

Guo

et al. 2020

J. Am. Chem. Soc.

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An enantioselective total synthesis of (−)-batrachotoxinin A is accomplished based on a key photoredox coupling reaction and the subsequent local-desymmetrization operation. After the expedient assembly of the highly oxidized steroid skeleton, a delicate sequence of redox manipulations was carried out to deliver a late-stage intermediate on gram scaleand ultimately (−)-batrachotoxinin A in an efficient manner.

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A Generic and Reproducible Route to Homo- and Heteroannular Bicyclic β-Diketones via Knochel-Type 1,4-Conjugate Additions to α,β-Unsaturated Cycloalkenones

Cited by 3 publications

References 15 publications

Short Syntheses of some ‘Decalin‐1,8‐diones’ and their Derivatives: Breaking the Pretended Symmetry

Short Syntheses of some ‘Decalin‐1,8‐diones’ and their Derivatives: Breaking the Pretended Symmetry

Access to Functionalized Quaternary Stereocenters via the Copper-Catalyzed Conjugate Addition of Monoorganozinc Bromide Reagents Enabled by N,N-Dimethylacetamide

Total Synthesis of (−)-Batrachotoxinin A: A Local-Desymmetrization Approach

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