Approaches to the Total Synthesis of the Montanine (Amaryllidaceae) Alkaloids. Preparatiion of Isomeric 3-Aryloctahydroindoles

Sánchez, I. H.; Larraza, M. I.; Rojas, I.; Brena, F. K.; Flores, Humberto; Jankowski, Krzysztof

doi:10.3987/r-1985-12-3033

Cited by 19 publications

(4 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The present reaction is potentially useful in organic synthesis. For example, nitro compound 5a was readily converted into 3-phenyloctahydroindole, and we also found that, in the presence of Pd/C, 5a was easily hydrogenated into the corresponding nitrone 6 in 95% yield without loss of ee (eq 1) 3c. The structure of nitrone 6 was determined by NMR, mass spectra and further confirmed by X-ray analysis, which was in full accordance with the relative configuration as described above (Figure ).…”

supporting

confidence: 80%

Pyrrolidine−Thiourea as a Bifunctional Organocatalyst: Highly Enantioselective Michael Addition of Cyclohexanone to Nitroolefins

et al. 2006

View full text Add to dashboard Cite

show abstract

supporting

confidence: 80%

Pyrrolidine−Thiourea as a Bifunctional Organocatalyst: Highly Enantioselective Michael Addition of Cyclohexanone to Nitroolefins

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Relative and absolute configurations of the products were determined by comparison with the known 1 H NMR, chiral HPLC analysis, and optical rotation values. Compounds reported in Table 2, entries 1 [4] , 2 [5] , 3 [6] , 6 [7] , 8 [8] , 9 [ 9] , 10 [10] are known.…”

Section: Typical Procedures For Michael Addition Reactionsmentioning

confidence: 99%

“…-2-nitroethyl)cyclohexanone 5f [7] : [8] : (Procedure B) reaction time: 38 h (87% yield); ee was determined by HPLC analysis (Chiralcel AD-H, i-PrOH/hexane = 5/95, 0.7 mL/min, 214 nm; t r (minor) = (S)-2-((S)-3-methyl-1-nitrobutan-2-yl)cyclohexanone 5j [10] : (Procedure B) reaction time: 6 d (63% yield); ee was determined by HPLC analysis (Chiralcel AD-H, i-PrOH/hexane = 10/90, 1.0 mL/min, 214 nm; t r (major) = 6.31 min, t r (R)-5-nitro-4-phenylpentan-2-one 5k [11] : (3S,4R)-3-methyl-5-nitro-4-phenylpentan-2-one 5ma [11] (R)-6-nitro-5-phenylhexan-3-one 5mb [11] (R)-2,2-dimethyl-4-nitro-3-phenylbutanal 5n [12] (3R,3aS)-3-phenyl-3,3a,4,5,6,7-hexahydro-2H-indole 1-oxide 7 [13] : A suspension of Pd/C (8 mg) and 5a (50 mg) in MeOH (5 mL) was stirred at room temperature under 3 atm hydrogen atmosphere. After being stirred for 12 h, the mixture was filtrated through a pad of Celite and the filtration was concentrated in vacuo, the residue was purified by column chromatography on silica gel to afford desired product 7 (43 mg, 95%…”

Section: Br (S)-2-((r)-1-(4-bromophenyl)mentioning

confidence: 99%

Pyrrolidine—Thiourea as a Bifunctional Organocatalyst: Highly Enantioselective Michael Addition of Cyclohexanone to Nitroolefins.

et al. 2006

View full text Add to dashboard Cite

show abstract

“…We were gratified to find that the cascade was also applicable to aliphatic (entry 2, 4 → 5 10 ), α,β-unsaturated (entry 3, 6 → 7 10 ), and electron-rich (entry 4, 8 → 9 , and entry 5, 10 → 11 ) aldehydes. In all, only exocyclic olefins were generated including 5 , the thermodynamically less-stable positional isomer.…”

mentioning

confidence: 99%

Ring Expansion/Homologation−Aldehyde Condensation Cascade Using tert-Trihalomethylcarbinols

Falck

Reddy

et al. 2006

Org. Lett.

View full text Add to dashboard Cite

Treatment of cyclic tert-trihalomethylcarbinols with CrCl 2 in THF/HMPA in the presence of aryl or aliphatic aldehydes initiates a cascade sequence of one carbon ring expansion-olefination affording conjugated exo-cyclic ketones. Acyclic tert-trihalomethylcarbinols undergo a comparable cascade of one carbon homologation-olefination.Trihalomethylcarbinols and their derivatives are a diverse 1 and readily accessible class of functionalized alcohols. 2 Their reduction, inter alia, electrochemical, 3 zero-valent metals/ metal salts, 4 or aqueous Cr(II), 5 principally induces elimination to the corresponding 1,1-dihaloölefin. However, our laboratories recently observed that sec-trihalomethylcarbinol derivatives follow a different reaction manifold when reduced with Cr(II) salts in THF leading stereoselectively to (Z)-α-haloenol esters and (Z)-β-haloenol ethers. 6 We consequently examined the behavior under similar conditions of tert-trihalomethylcarbinols in the presence of aldehydes and report herein a cascade sequence 7 of one carbon ring expansion/ homologation-olefination affording conjugated ketones. 8The cascade sequence was optimized using carbinol 1 9 (X = Cl) and benzaldehyde 2 as the test system. The best yield of adduct 3 10 was obtained using CrCl 2 (6 equiv) in THF/HMPA (2:1) at 40 °C (Table 1, entry 1). Using the tribromo-version of 1 (X = Br), the results were identical, except the reaction only required 2 h instead of the 4 h when X = Cl. The output of j.falck@utsouthwestern.edu; mioskow@aspirine.u-strasbg.fr. † University of Texas Southwestern. ‡ Université Louis Pasteur.Supporting Information Available Synthetic procedures, analytical data, X-ray files, and 1 H/ 13 C spectra for all new compounds. This material is available free of charge via the Internet at http://pubs.acs.org. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript 3 did not improve using a lower THF/HMPA ratio (i.e., 1:1) and it decreased linearly as the ratio increased in favor of THF. Other solvents or their combinations, e.g., THF only, DMF, EtOAc, dioxane, and HMPA, were not satisfactory. There was also a strict dependence on the amount of CrCl 2 ; 5 and 4 equivalents gave 3 in 51% and 30% yield, accordingly. Efforts to use fewer equivalents of CrCl 2 by coupling the reaction to a regeneration system showed promise, but clearly need further improvement. For instance, under otherwise identical conditions as entry 1, CrCl 2 (1 equiv)/Mn powder (8 equiv) and CrCl 2 (1 equiv)/Fe powder (10 equiv) gave rise to 3 in 58% and 42% yield, respectively.We were gratified to find that the cascade was also applicable to aliphatic (entry 2, 4→ 5 10 ), α,β-unsaturated (entry 3, 6 → 7 10 ), and electron rich (entry 4, 8 → 9 10 and entry 5, 10 → 11 11 ) aldehydes. In all, only exo-cyclic olefins were generated including 5, the thermodynamically less stable positional isomer. Notably, the yield of adduct, as demonstrated in the condensation of 1 with 10 (entry 5), could be ameliorated utilizing a mod...

show abstract

Approaches to the Total Synthesis of the Montanine (Amaryllidaceae) Alkaloids. Preparatiion of Isomeric 3-Aryloctahydroindoles

Cited by 19 publications

References 0 publications

Pyrrolidine−Thiourea as a Bifunctional Organocatalyst: Highly Enantioselective Michael Addition of Cyclohexanone to Nitroolefins

Pyrrolidine−Thiourea as a Bifunctional Organocatalyst: Highly Enantioselective Michael Addition of Cyclohexanone to Nitroolefins

Pyrrolidine—Thiourea as a Bifunctional Organocatalyst: Highly Enantioselective Michael Addition of Cyclohexanone to Nitroolefins.

Ring Expansion/Homologation−Aldehyde Condensation Cascade Using tert-Trihalomethylcarbinols

Contact Info

Product

Resources

About