6,7-Benzomorphans. Stereospecific synthesis of 2,9.alpha.- and 2,9.beta.-dimethyl-2'-methoxy-6,7-benzomorphans

Gless, Richard D.; Rapoport, Henry

doi:10.1021/jo01322a028

Cited by 28 publications

(3 citation statements)

References 46 publications

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“…When the reaction mixture was quenched with excess formic acid and allowed to warm to ambient temperature, amine 22 was isolated in 86% yield. Reports of the partial reduction of a pyrrolidin-2-one derivative to its aminol are rare. , The low reactivity of the carbonyl relative to the metalated aminol intermediates results either in over-reduction to the pyrrolidine or return of unreacted starting material . After significant optimization, we achieved single hydride delivery with DIBAL in toluene at −20 °C.…”

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confidence: 99%

Total Synthesis of (−)-Nakadomarin A

2009

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A short and highly stereoselective synthesis of (-)-nakadomarin A has been developed using combinations of catalyst-controlled bond formations, one-pot multistep procedures, and powerful route-shortening reaction cascades. Several unprecedented chemical transformations were developed, including a highly Z-selective, eight-membered-ring-forming intramolecular Julia-Kocienski reaction, a highly diastereoselective intramolecular furan/iminium ion cyclization, and a sulfonic acid-controlled Z-selective macrocyclic ring-closing metathesis. In conjunction with a diastereoselective nitro olefin Michael addition under bifunctional organocatalysis and a nitro-Mannich/lactamization cascade, these transformations allowed the construction of this architecturally complex natural product in significant quantities in 12 steps (longest linear sequence) from commercially available starting materials.

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Total Synthesis of (−)-Nakadomarin A

2009

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“…Tertiary a-cyanoenamines 2 are synthesized by reaction of cyanide with a-chloroenamines lo), amide chlorides lo), thioimidate salts 11) and ynaminesl2), while other general synthetic methods involved dehydrohalogenation of 0-halo-a-(dialkylamino)nitriles, the latter being obtained from a-haloaldehydes13 -16) or enamines 16,17). Alternative valuable entries to a-cyanoenamines are N-alkylation of secondary a-cyanoenamines 18), condensation of carbonyl compounds with the anion derived from diethyl 1-cyano-1-(dimethy1amino)methanephosphonate 19) or a-(N-methylanilino)-a-(trimethylsilyl)acetonitrilez0).…”

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Synthesis of α‐Cyanoenamines by Cyanation of α‐Bromoimmonium Bromides and Dehydrobromination of β‐bromo‐α‐(dialkylamino)nitriles

et al. 1983

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The reaction of a-bromoimmonium bromides 4 with potassium cyanide in dimethylformamide gave rise to P-bromo-a-(dia1kylamino)nitriles 5, which were dehydrobrorninated in various basesolvent systems to afford (E)-and (Z)-a-cyanoenamines 2. An adaption of a previously published preparation of a-cyanoenamines starting from aldehydes oia enamines led to an improved, efficient and fast synthesis of the title compounds. Synthese von a-Cyanenaminen durch Cyanierung von a-Bromimmonium-bromiden und Dehydrobromierung von p-Brom-a-(dialky1amino)nitrilenDie Reaktion der a-Bromimmonium-bromide 4 mit Kaliumcyanid in Dimethylformamid gibt P-Brom-a-(dialky1amino)nitrile 5, die in verschiedenen Base-Losungsmittel-Systemen zu (E)-und (2)-a-Cyanenaminen 2 dehydrobromiert werden. Eine Modifizierung einer kiirzlich veroffentlichten Synthese von a-Cyanenaminen 2 aus Aldehyden iiber Enamine fiihrte zu einer verbesserten und schnellen Methode fur die Darstellung der Titelverbindungen. a-Cyanoenamines (1, 2) are a group of functionalized olefins which contain a sp2 carbon atom, geminally substituted with an electron-withdrawing and electrondonating substituent.Especially during the last decade efforts have been undertaken for the synthesis of a-cyanoenamines, which were shown to be valuable synthons in synthetic organic chemistry (vide infra). A variety of synthetic methods are now available to synthesize secondary a-cyanoenamines 1 and tertiary a-cyanoenamines 2. Secondary a-cyanoenamines 1 are synthesized by reaction of a-chloroaldimines with potassium cyanide* -4, or, to a lesser extent, by dehydrohalogenation of appropriate P-halo-a-(alky1amino)nitriles -').Only in the former case are secondary a-cyanoenamines 1 generally accessible, while in the latter case an additional isomerism to the tautomeric imidoyl cyanides prohibits isolation of pure a-cyanoenamines.

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“…Functionalized primary a-cyanoenamines 1 (R = H) are available from cyanide addition to dihaloa~etonitrile~~~). Tertiary a-cyanoenamines 2 are synthesized by reaction of cyanide with a-chloroenamines lo), amide chlorides lo), thioimidate salts 11) and ynaminesl2), while other general synthetic methods involved dehydrohalogenation of 0-halo-a-(dialkylamino)nitriles, the latter being obtained from a-haloaldehydes13 -16) or enamines 16,17). Alternative valuable entries to a-cyanoenamines are N-alkylation of secondary a-cyanoenamines 18), condensation of carbonyl compounds with the anion derived from diethyl 1-cyano-1-(dimethy1amino)methanephosphonate 19) or a-(N-methylanilino)-a-(trimethylsilyl)acetonitrilez0).…”

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confidence: 99%