The Synthesis of New S- and N,S-Substituted Halo Nitro Dienes by the Reactions of 1-Bromo-1,2,4,4-tetrachloro-3-nitrobuta-1,3-diene with Thiols and Cyclic Amines

The substituted products alkyl(aryl)thio-tetrahalo-3-nitrobuta-1,3-dienes 3a–b were obtained from the reactions of 1-bromo-1,2,4,4-tetrachloro-3-nitrobuta-1,3-diene (1) with thiols. Further reactions of the substituted product alkyl(aryl)thio-tetrahalo-3-nitrobuta-1,3-dienes 3a–b in dichloromethane reacted with piperazine derivatives and morpholine to generate 5a–b and 7a–l. The structures of the new compounds were determined by microanalysis and spectroscopic data.     

N,N-dihalophosphoramides-XV: The addition of diethyl N,N-dichlorophosphoroamidate (DCPA) to conjugated 1,3-dienes

The addition of DCPA to several conjugated 1,3-dienes has been studied. The reaction was found to proceed in dichloromethane and was spontaneously or photolytically initiated depending on the structure of the dienes. N-chloro adducts, formed upon addition, could be reduced “in situ” with sodium sulphite solution to give the corresponding diethyl N-(chloroalkenyl)posphoroamidates. Addition of DCPA to terminal double bond 1,3-dienes (butadiene, isoprene and 2,3-dimethyl-1,3-butadiene) leads regiospecifically to (E)-1,4-adducts. Similarly, 1,4-addition is also observed for 1,3-cyclohexadiene. Reaction of DCPA with nonterminal double bond 1,3-dienes (trans-piperylene, 4-methyl-1,3-pentadiene, 2,5-dimethyl-2,4-hexadiene and 1,4-diphenyl-1,3-butadiene) usually affords a mixture of adducts. Spectral data and chemical transformations pertinent to the proof of structure of DCPA addition products are presented. A possible mechanism for the addition is discussed.     

The addition of methylborylene to acetylenes: Synthesis of 1,4-diboracyclohexa-2,5-dienes,and of a borirene and a diboretene derivative

The synthesis of 1,4-dimethyl-2,3,5,6-tetra-n-alkyl-1,4-diboracyclohexa-2,5-dienes from the reaction of di-n-alkylacetylenes with the methylborylene-generating system 2C₈K/MeBBr₂ is described. A mechanism for these reactions is proposed. The addition of methylborylene to di-t-butylacetylene results in the formation of 1-methyl-2,3-di-t-butylborirene and of 1,3-dimethyl-2,4-di-t-butyl-1,3-diboretene.     

[2,3] Sigmatropic Rearrangement of Ethyl 2-(Diethoxyphosphoryloxy) Allyl Sulfoxides and Selenoxides. Synthetic Applications

Abstract

We have previously described regio- and stereospecific synthesis of ally1 selenides I and ally1 sulfides 2 [1]. We now report on the application of 1 and 2 as attractive precursors of new, functionalized: allylic alcohols 3, α-hydroxy ketones 4 and I, 3-dienes 5. 1 and 2 are transformed by oxidation into corresponding ally1 selenoxide and sulfoxide, which display stereospecific [2,3] sigmatropic rearrangement providing after hydrolysis the allylic alcohols 3. Trans configuration of 3 was established by X-ray analysis. In some cases the rearrangement is accompanied by elimination giving the 1,3-dienes 5. Compounds 3 and 5 can be easily separated by column chromatography Dephosphorylation of 3 afforded the α-hydroxy ketones 4.     

Oxidative Coupling via Organocopper Compounds

The type of reaction described here, which achieved preparative importance before the turn of the century in the form of the Glaser reaction, has found new applications in recent years: Syntheses of 1,3-dienes, 2,3,6,7-tetraaza-1,3,5,7-tetraenes, 2,3-diaza-1,3-dienes, hydrazine derivatives, bis(heteroallyl) compounds, hetarenes, polyhetarenes, cyclopolyarenes, protophanes, phanes, and heteraprotophanes. The reaction, which consists in the metalation of the starting substance followed by oxidative coupling of the metal derivative, merits special preparative interest when several successive coupling processes are possible (e. g. polyyne, polyarene, cyclopolyarene, and protophane syntheses). The main factors limiting its applicability are the high thermal stability of some organic copper compounds and the disproportionation of the ligands that frequently occurs as a competing reaction. Selective asymmetric linkages are not generally possible by this method.     

Fluorophosphaalkenes - New Versatile Reagents

Abstract

The synthesis of substituted fluorophosphaalkenes RP=CFR′ with a variety of groups R and R′ is discussed. The reactivities (self-addition, HX addition, [2+4] cycloaddition with 1,3-dienes) and the coordination chemistry of selected compounds have been explored.     

Catalytic cyclometalation reaction of unsaturated compounds in synthesis of magnesa- and aluminacarbocycles

The investigation results on design and application of the new catalytic cyclometalation reaction of olefins, dienes, acetylenes and allenes with Al, Mg and halogen alkyls mediated by Ti or Zr based metallocene catalysts to produce novel classes of cyclic organometallics namely aluminacyclopropanes, aluminacyclopropenes, aluminacyclopentanes, aluminacyclopentenes, aluminacyclopenta-2,4-dienes, magnesacyclopentanes, magnesacyclopentenes, magnesacyclopenta-2,4-dienes as well as metallamacrocycles are summarized and systematized. Selected literature data on thermal synthesis of cyclic organoaluminum and organomagnesium compounds for comparison the efficiencies of catalytic and classic synthetic methods are given. Mechanistic aspects of catalytic cyclometalation of unsaturated compounds and chemical transformations of Al and Mg metallacycles are discussed.     

Tetracyanoethylene pi-complex chemistry. Indirect spectrophotometric determination of Diels-Alder-active 1,3-dienes

An indirect spectrophotometric method, based on the rapid Diels-Alder reaction between cisoid 1,3-dienes and tetracyanoethylene (TCNE) and the destruction of an aromatic-TCNE pi-complex, was developed to determine eleven 1,3-dienes in the 0.05-1.00 x 10(-3)M range. These dienes were: cyclopentadiene; 1,3-cyclohexadiene; trans-1,3-pentadiene; 2,4-dimethyl-1,3-pentadiene; trans-2-methyl-1,3-pentadiene; 2-methyl-1,3-butadiene; 9-methylanthracene; 9,10-dimethylanthracene; 1,6-diphenyl-1,3,5-hexatriene; 2,3-dimethyl-1,3-butadiene; and 1,4-diphenyl-1,3-butadiene. Three 1,3-dienes were determined in the 0.05-1 x 10(-4)M range: cyclopentadiene, trans-2-methyl-1,3-pentadiene, and anthracene. The limit of detection for cyclopentadiene in carbon tetrachloride solutions is 0.11 microg/ml. Fourteen 1,3-dienes were found to form stable pi-complexes and could not be determined by the proposed method. For these 1,3-dienes, the spectra of some of the complexes are reported; in addition, relative equilibrium constants for the pi-complexes of 2,5-dimethyl-2,4-hexadiene, cis-1,3-pentadiene, 4-methyl-1,3-pentadiene, and 1,3-cyclo-octadiene were estimated. An explanation of the transient colour in the 1,3-diene-TCNE Diels-Alder reaction is suggested.     

Synthesis of functionalized triarylmethanes by combination of FeCl3-catalyzed benzylations of acetylacetone with [3+3] cyclocondensations

Functionalized triarylmethanes are prepared in two steps by FeCl₃-catalyzed benzylation of acetylacetone to give 3-(diarylmethyl)pentane-2,4-diones and subsequent formal [3+3] cyclization of the latter with 1,3-bis(trimethylsilyloxy)-1,3-dienes.     

Regioselective synthesis of bis(silyl enol ethers) and bis(conjugated enones) through electron transfer from Mg metal

Treatment of α,β-unsaturated ketones with Mg metal in the presence of trimethylsilyl choride (TMSCl) brought about facile and regioselective reductive dimerization to give the corresponding bis(silyl enol ethers), 1,6-bis(trimethylsilyloxy)-1,5-dienes. Similar Mg-promoted reductive dimerization of 1,3-cyclic diketones in the presence of TMSCl followed by acid-catalyzed hydrolysis led to selective formation of the corresponding 1,6-diketo-2,4-dienes in moderate to good yields.     

Synthesis of functionalized triarylmethanes based on a ‘FeCl3-catalyzed benzylation/[3+3] cyclocondensation’ strategy

Functionalized triarylmethanes are prepared in two steps by FeCl₃-catalyzed benzylation of acetylacetone to give 3-(diarylmethyl)pentane-2,4-diones and subsequent formal [3+3] cyclization of the latter with 1,3-bis(trimethylsilyloxy)-1,3-dienes.     

Concise synthesis of multiply substituted stereodefined cis,cis-2,4-diene-1,6-dials, cis,cis-2,4-diene-1,6-diols and further applications

Reactions of 1,4-dilithio-1,3-dienes with DMF afforded multiply substituted stereodefined cis,cis-2,4-diene-1,6-dials in high yields. Treatment of these 1,6-dials with LiAlH₄ or RLi resulted in the formation of their corresponding 1,6-diols. These bifunctional compounds, cis,cis-2,4-diene-1,6-dials and -1,6-diols are otherwise not readily available. Further reaction of these 1,6-diols with an aldehyde catalyzed by strong acids led to the formation of oxacycles of novel structures.     

Synthesis of new sulfanyl-, sulfinyl-, and sulfonyl-substituted polychlorobuta-1,3-dienes

New R-sulfanyl-substituted polychlorobuta-1,3-dienes were synthesized by reactions of hexachloro-1,3-butadiene or 1,1,2,4,4-pentachlorobuta-1,3-diene with dimethylbenzenethiols, heptane-1-thiol, and 4-methyl-7-sulfanyl-2H-chromen-2-one. Some sulfides were oxidized to the corresponding sulfoxides and sulfones or brominated with bromine. Among the synthesized compounds, the coumarin derivative, 4-methyl-7-(1,2,3,4,4-pentachlorobuta-1,3-dien-1-ylsulfanyl)-2H-chromen-2-one showed fluorescence properties. 1,1′,1″-[3,4-Dichlorobuta-1,3-diene-1,1,4-triyltris(sulfanediyl)]tris(2,4-dimethylbenzene) reacted with potassium tert-butoxide in petroleum ether to afford a mixture of isomeric 1,1′,1″-[4-chlorobuta-1,2,3-triene-1,1.4-triyltris(sulfanediyl)]tris(2,4-dimethylbenzene) and 1,1′,1″-[2-chlorobut-1-en-3-yne-1,1,4-triyltris(sulfanediyl)]-tris(2,4-dimethylbenzene). The GC/MS method was found to be useful for the separation of some sulfanyl-substituted butadiene isomer mixtures. The synthesized compounds were characterized by elemental analyses, mass spectrometry, UV-Vis, IR, and NMR (¹H, ¹³C) or fluorescence spectroscopy.     

Stereoconvergent Synthesis of Z-1,3-Disubstituted-1,3-Dienes by Uphill Photocatalysis

A variety of 1-aryl-1,3-dienes were isomerized from E to Z isomers by photocatalysis using Ru(bpy)₃[PF₆]₂ and blue LED light. Enrichment of the Z-isomer is thought to occur by selective triplet energy transfer from the photocatalyst to the stereoisomeric mixture. The 1,3-diene starting materials are easily made by catalytic ene-yne metathesis (EYM). To access 1,3-diene Z-stereoisomers directly, a one pot procedure was developed. Additional 1,3-dienes were investigated for both isomerization and Z-enrichment. The combination of cross EYM with photocatalysis allows for the stereoconvergent synthesis of Z-1,3-dienes.     

Cycloaddition reactions of 2,4-diphenyl-1,3-diazabuta-1,3-dienes with isocyanates and isothiocyanates

The cycloaddition reactions of 1-p-tolyl and 1-benzyl- 2,4-diphenyl-1,3-diazabuta-1,3-dienes with a variety of aryl and alkyl isocyanate and isothiocyanate are described. The reaction mechanism is also discussed.     

[f]-Fused purine-2,6-diones: Synthesis of new [1,3,5]- and [1,3,6]-thiadiazepino-[3,2-f]-purine ring systems

Summary 6-Phenyl-1,3-dimethyl-2,4-dioxo-1,2,3,4,8,9-hexahydro-[1,3,5]-thiadiazepino-[3,2-f]-purine (5) was obtained by a three-step synthesis from 8-mercapto-1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione (1) and 2-(benzoylamino)-ethyl chloride (2)via 8-(benzoylaminoethylthio)-1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione (3) and its chloromido derivative4. The analogous 9-phenyl-1,3-dimethyl-2,4-dioxo-1,2,3,4,6,7-hexahydro-[1,3,6]-thiadiazepino-[3,2-f]-purine (7) was synthesized either from compound1 and N-(2-chloroethyl)-benzimido chloridevia N-(chloroethyl)-S-(1,3-dimethyl-2,4-dioxo-1,2,3,4-tetrahydro-7H-purin-8-yl)-benzothioimide (6), or alternatively from 7-(2-benzoylaminoethyl)-8-bromo-1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione (9), its 8-mercapto derivative10 and the corresponding chloroimido compound11 being the intermediates.Part of this paper was presented as a preliminary report at the Congress of Czech and Slovak Chemical Societies, Olomouc, Czech Republic, September 13–16, 1993     

Palladium-catalyzed cross-coupling of vinylic tellurides and potassium vinyltrifluoroborate salt: synthesis of 1,3-dienes

Here we report an ultrasound-assisted synthesis of stereodefined 1,3-dienes by Suzuki-Miyaura cross-coupling reactions of vinylic tellurides and potassium β-styryl trifluoroborate salt.     

SYNTHESES WITH DIKETO SELENIDES

Abstract

We report a) a modified synthesis of diketo selenides, b) preparation of 2,5-diacylselenophenes by condensation of diketo selenides with glyoxal, c) preparation of poly-substituted selenophenes by intramolecular reductive coupling reaction of diketo selenides with low-valent titanium reagent under controlled conditions (0°C) followed by dehyration of the resulting 3,4-dihydroxyselenolanes, and d) formation of 2,5-dihydroselenophenes and 1,3-dienes by treatment of diketo selenides with the low-valent titanium reagent in refluxing tetrahydrofuran.     

Synthese und chemie von 4R-silacyclohexa-2,5-dienen und 4R-silacyclohexa-2,4-dienen

The 1(Z),4(Z)-1,5-dilithium-3R-3-methoxypenta-1,4-dienes, available by cleavage of 1,1-di-n-butyl-4R-4-methoxy-1-stannacyclohexane-2,5-dienes with n-BuLi in ether, react with dichlorosilanes (R′R″ SiCl₂; R′, R″ = H, alkyl, aryl, alkoxy) to give 1R′,1R″,4R-4-methoxy-1-silacyclohexa-2,5-dienes.Claevage of the ether group with BBr₃, BCl₃ or PCl₃ gives 6-chloro(bromo)-1-silacyclohexa-2,4-dienes or 1,5-dichloro-1-silacyclohexane-2,4-dienes, respectively.Ether cleavage of 4R-4-methoxy-1-silacyclohexa-2,5-dienes with sodium results in the formation of 4R-1-silacyclohexadienyl anions, which can be hydrolyzed to give 1-silacyclohexa-2,4-dienes which reach further with trichloromethylsilane to give 6-trimethylsilyl-1-silacyclohexa-2,4-dienes.Phase transfer-catalyzed conversion of 1-chlorosilacyclohexadienes into the fluoro derivatives as well as further substitution reactions of 1-chlorosilacyclohexadienes are described.The ¹H NMR, ¹³C NMR, IR and mass spectra of the silacyclohexadienes are discussed.     

Chemodivergent,Regio- and Enantioselective Cycloaddition Reactions between 1,3-Dienes and Alkynes

Alkynes and 1,3-dienes are among the most readily available precursors for organic synthesis. We report two distinctly different, catalyst-dependent, modes of regio- and enantioselective cycloaddition reactions between these classes of compounds providing rapid access to highly functionalized 1,4-cyclohexadienes or cyclobutenes from the same precursors. Complexes of an earth abundant metal, cobalt, with several commercially available chiral bisphosphine ligands with narrow bite angles catalyze [4+2]-cycloadditions between a 1,3-diene and an alkyne giving a cyclohexa-1,4-diene in excellent chemo-, regio- and enantioselectivities. In sharp contrast, complex of a finely tuned phosphino-oxazoline ligand promotes unique [2+2]-cycloaddition between the alkyne and the terminal double bond of the diene giving a highly functionalized cyclobutene in excellent regio- and enantioselectivities.