Imino Diels–Alder reaction of 2-t-butyldimethylsilyloxycyclohexadiene: isolation of an azabicyclo[2.2.2]octene silyl enol ether adduct

1988 ◽  
Vol 0 (24) ◽  
pp. 1601-1602 ◽  
Author(s):  
Timothy N. Birkinshaw ◽  
Alethea B. Tabor ◽  
Andrew B. Holmes ◽  
Paul R. Raithby
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Enol Ether ◽  
Diels Alder Reaction ◽  
Silyl Enol Ether

The Kobayashi Synthesis of (-)-Norzoanthamine

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Conjugate Addition ◽  
Alder Reaction ◽  
Diels Alder ◽  
Enol Ether ◽  
Enantiomerically Pure ◽  
Quaternary Centers ◽  
Quaternary Center ◽  
Silyl Enol Ether ◽  
Starting Point ◽  
Open Face

The Zoanthus alkaloids, exemplified by (-)-norzoanthamine 3a and zoanthamine 3b, show promising activity against osteoporosis. Susumu Kobayashi of the Tokyo University of Science assembled (Angew. Chem. Int. Ed. 2009, 48, 1400; Angew. Chem. Int. Ed. 2009, 48, 1404) the challenging tricyclic core of 3a employing the intramolecular Diels-Alder cyclization of 1 to 2. The cyclopentane of 1 served as useful scaffolding, even though it was cleaved en route to 3a. The cyclohexane ring of 1 has five of its six positions substituted, including three that are alkylated quaternary centers. The starting point for the preparation of 1 was the enantiomerically-pure Hajos-Parrish ketone 4, containing the first of the those quaternary centers. Conjugate addition of MeLi established the second quaternary center. The less stable endo alkyl branch of 1 was installed by conjugate addition to the more reactive α-methylene ketone of the cross-conjugated 5, followed by kinetic quench. Addition of vinyl cuprate across the open face of the enone 7 then established the final quaternary center, setting the stage for the intramolecular Diels-Alder reaction. The silyl enol ether from the cyclization of 1 was not stable, so it was directly oxidized to the enone 2. The keto phosphonate 16 for the last two rings of 3a was prepared from the previously-reported crystalline glutamic acid-derived mesylate 12. Reduction and homologation delivered the ester 14, that was condensed with the phosphonate anion 15 to give 16. The congested cyclopentanone 17, derived from 2, was most efficiently deprotonated with n -BuLi. Exposure of the resulting silyl enol ether to ozone led to the α-hydroxylated product 18. Unexpectedly but happily, oxidative cleavage of 18 delivered, after deprotection and reprotection, the more congested aldehyde 19. This cleavage may be proceeding by tautomerization of 18 to the regioisomeric keto alcohol. The aldehyde 19 was condensed with the keto phosphonate 16, to give, after hydrogenation, the keto lactone 20. A series of oxidation state adjustments then completed the synthesis of (-)-norzoanthamine 3a.

Iodine-promoted imino-Diels–Alder reaction of fluorinated imine with enol ether: synthesis of 2-perfluorophenyl tetrahydroquinoline derivatives

Tetrahedron ◽  
2010 ◽  
Vol 66 (4) ◽  
pp. 913-917 ◽  
Author(s):  
Guifang Jin ◽  
Jingwei Zhao ◽  
Jianwei Han ◽  
Shizheng Zhu ◽  
Jianmin Zhang
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Enol Ether ◽  
Diels Alder Reaction ◽  
Ether Synthesis

Synthesis and transannular Diels–Alder reaction of a 13-membered macrocyclic triene having a tetrasubstituted enol ether as dienophile

1990 ◽  
Vol 68 (3) ◽  
pp. 404-411 ◽  
Author(s):  
Gervais Bérubé ◽  
Pierre Deslongchamps
Keyword(s):  
Organic Synthesis ◽  
Alder Reaction ◽  
Diels Alder ◽  
The Other ◽  
Enol Ether ◽  
Diels Alder Reaction ◽  
Other Hand ◽  
Tricyclic Compounds

The syntheses of the acyclic triene trans–trans–cis27 and trans–trans–trans31 are described. Macrocyclization and concomitant transannular Diels–Alder reaction were performed with the chloride derivative obtained from the trans–trans–cis triene alcohol 27 yielding a mixture of the tricyclic compounds trans–syn–trans33 and cis–syn–cis34. On the other hand, macrocyclization of the chloride derived from trans–trans–trans triene 31 was not successful. Keywords: transannular process, Diels–Alder reaction, macrocyclic triene, macrocyclization, tricyclic compounds, organic synthesis.

Total Synthesis of Lycoposerramine-R

Synlett ◽  
2018 ◽  
Vol 29 (18) ◽  
pp. 2377-2380
Author(s):  
Satoshi Yokoshima ◽  
Shinya Watanabe ◽  
Masatsugu Ishikawa ◽  
Toshimune Nomura ◽  
Tohru Fukuyama
Keyword(s):  
Total Synthesis ◽  
Alder Reaction ◽  
Diels Alder ◽  
Quaternary Carbon ◽  
Enol Ether ◽  
Ethynyl Group ◽  
Diels Alder Reaction

A total synthesis of lycoposerramine-R was accomplished. The synthesis featured a Claisen–Ireland rearrangement to install a two-carbon unit, and a hetero-Diels–Alder reaction to form a cyclic enol ether that reacted with an ethynyl group to construct a cis-hydrindane core containing a quaternary carbon. A 2-pyridone synthesis using 2-(phenylsulfinyl)acetamide was used to complete the synthesis.

Enantioselective Synthesis of Epi-Emetine Analogues: Control of the Facial Selectivity in a Three-Component Domino Knoevenagel-Hetero-Diels-Alder Reaction*

2004 ◽  
Vol 59 (4) ◽  
pp. 468-477 ◽  
Author(s):  
Lutz F. Tietze ◽  
Nils Rackelmann
Keyword(s):  
Main Product ◽  
Enantioselective Hydrogenation ◽  
Alder Reaction ◽  
Diels Alder ◽  
Enantioselective Synthesis ◽  
Enol Ether ◽  
Meldrum’S Acid ◽  
Chiral Catalyst ◽  
Diels Alder Reaction ◽  
Facial Selectivity

AbstractThe domino Knoevenagel-hetero-Diels-Alder reaction of the aldehyde rac-8, Meldrum’s acid 2 and enol ether 3 leads to the cycloadduct rac-17 as the main product which in a second domino process was transformed into the benzoisoquinolizidine rac-18 by solvolysis, hydrogenolysis, condensation and hydrogenation; rac-18 was used as a substrate for the synthesis of the two diastereomeric epiemetine analogues 9 and 10 with > 96% ee (9) and 80% ee (10), respectively, by condensation with the phenylethylamine 23, Bischler-Napieralski reaction and “enantioselective” hydrogenation using the chiral catalyst (R,R)-26.

Sign in / Sign up

Export Citation Format

Share Document