Stereochemistry of cycloadducts from 3,4-dihydro-6,7-dimethoxyisoquinoline ylide and olefins

Cycloaddition of 2-methoxycarbonylmethyl-3,4-dihydro-6,7-dimethoxyisoquinolinium ylide with various E-substituted olefin type dipolarophiles gave products of 10b-H, 1-H, 2-H and 3-H α,α,β,β-relative configuration with one exception. Relative configuration of compounds prepared has been determined by 1D and 2D ¹H and ¹³C nmr techniques. It has also been detected that a triple trans ? cis-1 ? cis-2 conformation equilibrium exists in solution.     

Synthesis and Stereochemistry of 4-Amino-2-Phenyl-1,2,3,4-Tetrahydroquinoline

Cis and trans-isomers of the 4-amino-2-phenyl-1,2,3,4-tetrahydroquinoline were synthesized. The relative stereochemistry of the isomers was determined by ¹H-NMR.     

Highly selective synthesis of hydrazones and indoles from olefins

Reaction of aliphatic olefins with synthesis gas and hydrazines in the presence of rhodium phosphine catalysts leads directly to the corresponding hydrazones. Applying Iphos as ligand good to excellent yields and high chemo- and regioselectivities were obtained in toluene under mild conditions. In case of aromatic hydrazines in situ Fischer indole synthesis can be combined with the new hydrazone preparation to give substituted indoles directly from olefins.     

Stereochemistry of addition of mercury salts to alkynes

Reactions of Hg(OOCR)₂ (R=Et, Prⁿ, Prⁱ, and Buⁿ) with methylphenylacetylene (with the corresponding acids as solvents) give mixtures ofcis- andtrans-adducts. The quantity of thecis-adduct increases with increase in the length of the acyl substituent.syn-Addition also occurs in the acetoxymercuration ofm-chlorophenyl(methyl)acetylene and 1-methoxybut-2-yne; in the latter case, this route predominates. The stereochemistry of the reaction can also depend on the ratio of the reactants. It is proposed that the reaction occurs by several schemes in which these factors manifest themselves in different degrees. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No.8, pp. 1617–1624, August, 1998.     

Use of quinolinium salts in parallel synthesis for the preparation of 4-amino-2-alkyl-1,2,3,4-tetrahydroquinoline

Compounds of pharmacological interest containing a 4-amino-2-alkyl-1,2,3,4-tetrahydroquinoline core structure were prepared starting from 4-chloroquinoline. This has been executed both in solution with a 1-benzyl-4-chloroquinolinium salt and on a solid support with a 1-(4-benzyloxybenzyl-PS)-4-chloroquinolinium resin as key intermediates. Diversification of such intermediates was accomplished through N-arylation of position 4 and subsequent nucleophilic addition of Grignard reagents of position 2 to deliver the expected 4-amino-2-alkyl-1,2,3,4-tetrahydroquinolines in 20-60% yields. The methods described within clearly demonstrate that the quinolinium salts are very efficient intermediates for parallel synthesis.     

Stereochemistry and transformation of dihydrothebain in the bain synthesis from labelled thebaines

The complete stereochemistry of the Δ⁶-dihydrothebaine → 7-bromodihydrocodeinone dimethyl ketal → codeinone dimethyl ketal → thebaine sequence of transformations has been elucidated by NMR studies of the isotopically labeled compounds prepared using diimide-d₂, methyl hypobromite-[¹⁴C], and methyl hypobromite-d₃. Final elimination of methanol from codeinone dimethyl ketal proceeds in a stereospecific manner: cis under acid catalysis with POC1₃, and trans under alkaline catalysis with EtO^?. As a result of these reactions, variously isotopically labeled thebaines can be prepared.     

Direct synthesis of oxazolines from olefins and amides using t-BuOI

A new and simple method for the synthesis of oxazolines from readily accessible olefins and amides using tert-butyl hypoiodite is described; aromatic/aliphatic olefins and amides can be used in the reaction to give a variety of oxazolines.     

The synthesis of quaternary ammonium salts from ammonium salts and dialkyl carbonate

Quaternary ammonium salts were synthesized from ammonium salts and dialkyl carbonates over an ionic liquid catalyst 1-ethyl-3-methylimidazolium bromide.     

Stereochemistry in the synthesis and reaction of exo-glycals

Two general methods are explored for the stereoselective synthesis of exo-glycals. One method utilizes a nucleophilic addition of fully protected sugar lactones of gluco-, galacto-, and manno-types, followed by the subsequent dehydration, to give the desired exo-glycals with (Z)-configuration. The other method proceeds with selenylation of C-glycosides in a stereoselective manner. The subsequent selenoxide elimination also provides (Z)-exo-glycals. The prepared exo-glycal conjugated esters of either gluco- or manno-type react with allyl alcohol to give exclusively alpha-anomers.     

Photochemical synthesis of 1,2,3,4-tetrahydroisoquinolin-3-ones from N-chloroacetylbenzylamines

When N-chloroacetyl-3-hydroxybenzylamine (37) in aqueous acetonitrile was irradiated, both ortho and para photocyclizations with reference to the OH group occurred to give 7- and 5-hydroxy-3-oxo-1,2,3,4-tetrahydroisoquinolines (52,53). Similarly, 1-methylisoquinoline derivatives (54,55) were synthesized. N-Chloroacetyl-3,5-dihydroxybenzylamine (39) gave a single photoproduct, 5,7-dihydroxy-3-oxo-1,2,3,4-tetrahydroisoquinoline (56). These photocyclizations were smoothly extended to the synthesis of 1-benzyl, 1-(4′-methoxybenzyl)- and 1-(3′,4′,5′-trimethoxybenzyl)-isoquinoline derivatives (58～64).     

The palladium-catalyzed Heck arylation of olefins with arenediazonium salts as a sustainable strategy in organic synthesis

1. Download : Download high-res image (247KB)
2. Download : Download full-size image

     

Stereochemistry of heterocycles. XL. Stereochemistry of the synthesis of 2,3-dialkyloxetanes

It is shown that trans-2,3-dialkyloxetanes are formed from the erythro isomers of 2-alkyl-1,3-butanediols, whereas cis-2,3-dialkyloxetanes are formed from the threo isomers.See [1] for communication XXXIX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 164–168, February, 1976.