Showing papers by "Lambert Brandsma published in 2010"

Preparation, metallation and alkylation of allenyl ethers

Abstract: Propargyl ethers HCCCH2OR [R = alkyl or-CH(CH8)(OC2H5)] have been isomerized with good yields into the corresponding allenyl ethers CH2CCHOR by warming with potassium tert.-butoxide at 70°. These allenyl ethers can be metallated with butyllithium in ether or alkali amides in liquid ammonia. In ether, subsequent alkylation with alkyl halides R′Hal affords α-substituted allenyl ethers CH2CC(R′)OR. Alkylation in liquid ammonia produces a mixture of this same compound and the γ-substituted product R′CHCCHOR. In both cases reasonable yields are obtained. Sodamide and potassium amide quickly convert allenyl ethers CH2CCHOR into metallated propargyl ethers MCC-CH2OR (M = Na or K). If alkylation is not performed almost simultaneously with the metallation with sodamide or potassium amide, the only alkylation product obtained is R′CCCH2OR.

A versatile synthesis of allenic hydrocarbons. Evidence for an organocopper(III) intermediate

Abstract: A number of allenes RR1CCCHR22 have been prepared by interaction between acetylenic tosylates R1C≡CCHR2OTs, 1 (R1 = H, alkyl, aryl, H2CC(CH3) or CH3C≡C; R2 = H or t-C4H9) and organocopper(I) compounds “RCu” (formed from Grignard compounds RMgCl or RMgBr with R = alkyl, aryl or 2-thienyl and copper(I) bromide in tetrahydrofuran). If R = t-C4H9 the reaction with catalytic amounts of CuBr also gives good results. Significant amounts of C6H5CHCCH2 or C6H5CDCCH, are formed if C6H5CCCH2OTs is reacted with “CH3Cu” (from CH3MgCl and CuI) at −60° in tetrahydrofuran and the reaction mixture is quenched at low temperatures with methanol or deuteriomethanol. This finding is considered as evidence for the intermediate occurrence of a copper(III) derivative.

Chemistry of acetylenic ethers, 67: Allenyl thioethers from alkynyl thioethers

Abstract: The isomeric allenyl thioethers, III, are produced in good yield by treating 1-ethylthio-1-alkynes, I, with an equivalent amount of sodamide in liquid ammonia, followed by hydrolysis of the reaction mixture. The corresponding allenyl thioethers alkylated in the 1-position, IV, are obtained, also in good yield, by adding primary or secondary alkyl halides to the reaction product of sodamide and 1-ethylthio-1-alkynes, I.

Chemistry of acetylenic ethers 102: Reaction of di(1‐alkynyl) sulfides with sodium sulfide, selenide and telluride. Formation of 1,4‐dithiins, 1,4‐thiaselenins and 1,4‐thiatellurins

Abstract: Interaction between di(1-alkynyl) sulfides (1) and sodium sulfide, selenide or telluride in mixtures of liquid ammonia and methanol or dimethylformamide and methanol gives 1,4-dithiins (2), 1,4-thiaselenins (3) and 1,4-thiatellurins (4).

Chemistry of acetylenic ethers 70: Preparation of 1‐alkynyl thioethers and 1‐alkynyl selenoethers from sodium alkynylides, sulphur or selenium and alkyl halides

Abstract: A number of 1-alkynyl thioethers and selenoethers RCC-XR′ (XS or Se) have been prepared by reaction of sodium alkynylides, dissolved in liquid ammonia, with sulphur or selenium, followed by alkylation. 1,3-Enynyl thioethers, RCHCH-C≡C-SR′, ω,ω-diynyl thioethers R′S-C≡C-(CH2)n-C≡C-SR′ and 1,3-diynyl thioethers RC≡C-C≡C-SR′ also can be obtained in this manner. The yields are satisfactory, except in the case of the ethynyl thioethers HC≡C-SR′. Alkylselenoacetylenes HC≡C-Se R′ are not accessible by this method.

Base induced reactions of 1‐alkoxy‐ or l‐methylthio‐l‐(α‐ or β‐hydroxyalkyl)allenes. Formation of 3‐alkoxy‐ and 3‐methylthiodihydrofurans

Abstract: l-Alkoxy-l-(α-hydroxyalkyl)allenes R1CH=C=C(OR2)C(OH)R3R4 (Ia) have been converted with high yields into 3-alkoxy-2,5-dihydrofurans (II) using potassium tert-butoxide in dimethyl sulfoxide. Hydrolysis of II with dilute sulfuric acid afforded 3-oxotetrahydrofuran derivatives III. l-(β-Hydroxyalkyl)-l-methylthioallenes R1CH=C=C(SCH3)CH2CH2OH (IVb) and the analogous oxygen compounds IVa yielded 2-alkyl-3-methylthio-4,5-dihydrofurans (Vb) and a mixture of 3-methoxy-2-methyl-4,5-dihydrofurans (Va) and 3-methoxy-2-methylenetetrahydrofuran VI, respectively. The preparation of the hydroxyallenes is described.

Rearrangements of substituted propargyl vinyl sulfides: Formation of allenic dithioesters and their conversion into derivatives of 2H-thiopyran and thiopene

Abstract: Compounds of the general formula R1CH=C(SC2H5)S-CH2C2≡CR2 (II) (with R1=H, alkyl or aryl and R2=H or CH3) prepared by metallation of dithioesters R1CH2C(=S)SC2H5 (I) with potassium amide in liquid ammonia and subsequent reaction with R2C≡CCH2Br, rearrange at elevated temperatures. The first product is the allenic dithioester CH2=C=C(R2)-CH(R1)C(=S)SC2H5 (III), which can undergo cyclisation either to a 2 H-thiopyran derivative (IV, see reaction scheme) or to a substituted thiophene (V, see scheme I). The thiopyran formation is strongly accelerated by triethylamine, whereas (traces of) acids favour the cyclisation to thiophenes. Energies of activation for the conversion of II to III have been determined.

Chemistry of acetylenic ethers. LXI: A simple method for the preparation of acetylenic thioethers, selenoethers and telluroethers (Preliminary publication)

Abstract: The compounds mentioned in the title have been prepared in accordance with the reaction scheme below, in yields between 50 and 75 %.

Chemistry of acetylenic ethers 75: Isomerization of some 2‐alkynyl ethers into allenyl ethers with a note on the preparation of branched acetylenes

Abstract: 2-Alkynyl ethers of the types R′R″CH-CC-CH2OC2H5 and R′R″R″′C-CC-CH2OC2H5 (in which R′, R″ and R″′ are alkyl groups) have been converted by means of sodamide in liquid ammonia, in 70-95% yields, into the allenyl ethers R′R″CH C CH-OC2H5 and R′R″R″′C-CH C CH-OC2H5. Acid hydrolysis of the allenyl ethers afforded the trans-α,β-unsaturated .

Preparation of dithioesters from alkynethiolates and thiols: Evidence for the intermediate occurrence of thioketenes

Abstract: Dithioesters have been obtained in satisfactory yields by adding ethereal solutions of lithium alkynethiolates, RCCSLi, to an excess of a thiol. Thioketenes RCHCS are supposed to be intermediate species.

Chemistry of acetylenic ethers: 76 Preparation of compounds with a 1,3‐enyne system

Abstract: Ethers with the systems , CH3CCCH(OR)2, CH3CCCH(OR)3 or -CH2-CH2-CCOR undergo an elimination of ROH [R = alkyl, 2-alkynyl (-CH2CC-R′) phenyl, or 2-tetrahydropyranyl] with formation of 1,3-enyne derivatives, , on treatment with alkali amides in liquid ammonia. The cyclic ethers: and are isomerized under these conditions to the 1,3-enyne carbinols HCC-CHC(CH3)CH2OH and HCC-CHCH(CH2)4OH.

Conversion of 1‐alkyne‐1‐thiolates and ‐selenolates into thioketene and selenoketene precursors. Preparation of bis(trimethylsilyl)selenoketene, the first stable selenoketene

Abstract: Lithium 1-alkynethiolates and -selenolates RC≡CXLi (X = S, Se) have been converted with allyl bromide and with 1-bromo-2-butyne into the compounds H2C=CH-CH2-X-C≡C-R and CH3C≡C-CH2-XC≡C-R (R = t-C4H9, Me3Si; X = S, Se), respectively. Upon heating, only the sulfides H2C=CH-CH2-S-C≡C-R gave isolable thioketenes by [3,3]-sigmatropic rearrangement. The analogous selenoketene and the thioketene from the rearrangement of Me3Si-C≡C-X-CH2CCH3 are unstable. In the reaction of CH3C≡C-SeSiMe3 and t-C4H9C≡C-SeSiMe3 with diethylamine, giving the selenoamides C2H5C(Se)NEt2 and t-C4H9CH2C(Se)NEt2, the selenoketenes CH3CH=C=Se and t-C4H9CH=C=Se are the presumed intermediates. Pure bis(trimethylsilyl)selenoketene [Me3Si]2C=C=Se (7) was obtained in 80% yield from the reaction of Me3SiC≡C-SeLi and Me3SiCl at low temperatures.

Synthesis and some properties of 1‐alkenyl alkyl disulfides and di(1‐alkenyl) disulfides

Abstract: The synthesis of 1-alkenyl alkyl disulfides, R-CH=CH-S-S-R′, and di(l-alkenyl) disulfides, R-CH=CH-S-S-CH=CH-R, with R = H or alkyl and R′ = alkyl, is reported. Reaction of 1-alkenethiolates R-CH=CH-SLi(Na), prepared in situ by cleavage of 1-alkenyl alkyl sulfides with alkali metal in liquid ammonia, with S-alkyl alkanethiosulfonates, R′-S-SO2-R′ or alkyl thiocyanates, R′-SCN, affords 1-alkenyl alkyl disulfides in excellent yields. Reaction of alkenylmagnesium halides, R-CH=CH-SMgCl(Br), likewise leads to formation of 1-alkenyl alkyl disulfides, but yields are moderate. Treatment of l-ethylthio-2-propenylthioethene, CH3-CH=CH-S-CH=CH-S-C2H5, with podium amide in liquid ammonia, results in formation of sodium 1-propenethiolate which reacts with S-propyl propanethiosulfonate to give propenyl propyl disulfide in good yield. Oxidation in situ of 1-alkenethiolate anions with iodine affords the corresponding di-(l-alkenyl) disulfides.

A general method for the preparation of cumulenic ethers and thioethers

Abstract: Solutions of lithiated cumulenic ethers and bis-ethers R2CHCCC(Li)OR3 and R1OCHCCC(Li)OR3 can be obtained by treatment of the compounds R1OCH(R)2)CCCH2OR3 and R1OCH2CCCH(OR3)2 respectively with 2 equivalents of butyllithium in ether. Reaction of these solutions with H2O, D2O, methyl iodide, α-chloro-ethers or ketones gives the cumulenic compounds or their derivatives in good yields. Solutions of lithiated cumulenic thioethers R2CHCCC(Li)SR3 are obtained in an analogous way, but hydrolysis affords the isomeric enynic thioethers R2CHCHCCSR3 in addition to the expected cumulenic thioethers R2CHCCCHSR3. Elimination of R1OH from R1OC(R2)2CCCH(SR3)2 with 1 equivalent of C4H9Li leads to the cumulenic dithioacetals (R2)2CCCC(SR3)2.

Metallation of 1,3‐dienyl ethers and 1,3‐dienyl sulfides in the 1‐position

Abstract: 1,3-Dienyl ethers and the corresponding sulfides (CH2CHCHCHXR; XO, S; Ralkyl, phenyl) are readily metallated at C-1, using n-butyllithium and KO-t-Bu in tetrahydrofuran. 2H-Thiopyran can be lithiated at the 6-position with n-butyllithium and tetramethylethylenediamine in tetrahydrofuran. The various metallated compounds react smoothly with methyl iodide, methyl thiocyanate and acetaldehyde to give the expected derivatives. At about −20° a more than 95 % transformation of the metallated compound from cisCH2CHCHCHStBu into the trans-isomer occurs; with smaller R groups (isopropyl or ethyl) a less complete inversion is observed.

Chemistry of acetylenic ethers 72: Nucleophilic substitutions at sulphur and selenium in some alkynyl thioethers and alkynyl selenoethers

Abstract: Under the catalytic influence of bases, such as sodamide and sodium acetylide dissolved in liquid ammonia, ethylselenoacetylene, HCC-SeC2H5, disproportionates into bis(ethylseleno)acetylene, C2H5SeCCSeC2H5, while ethylthioacetylene remains unchanged under the same conditions. Bis(ethylseleno)acetylene and bis(ethylthio)acetylene react with phenyl-lithium in ether. The selenoether gives lithium ethylselenoacetylide, LiCCSeC2H5 or dilithium acetylide LiCCLi and ethyl phenyl selenide, C6H5SeC2H5, while the thioether is converted into lithium ethylthioacetylide, LiCCSC2H5 or dilithium acetylide and ethyl phenyl sulphide, C6H5SC2H5, and some phenylacetylene. Ethers of the type RCCSC2H5, in which R represents a tertiary butyl group or a phenyl group, are smoothly cleaved by a solution of potassium amide in liquid ammonia, RCCK being produced.

Chemistry of acetylenic ethers 110 a convenient synthesis of 1‐alkynyl ethynyl sulfides preparation of mono‐substituted 1,4‐dithiins, 1,4‐thiaselenins and 1,4‐thiatellurins

Abstract: 1-Alkynyl ethynyl sulfides RC≡CS-C≡CH (2) are easily accessible starting from 1-alkynyl trimethylsilylethynyl sulfides RC≡CS-C≡CSi(CH3)3 (1). When compounds 2 are treated with sodium sulfide, selenide or telluride in methanol 1,4-dithiins, 1,4-thiaselenins and 1,4-thiatellurins are obtained in good yields.

Syntheses and some reactions of aliphatic 1,2,3‐trienes

Abstract: Trienes of the type R(R′)CCCCH2 (R and R′ are H or alkyl) have been prepared in good to excellent yields from 1,4-dichloro-2-alkynes, R(R′)C(Cl)CCCH2Cl, and zinc dust or sodium iodide in dimethyl sulfoxide. The dichloro compounds were obtained from the corresponding 1,4-dihydroxy-2-alkynes and thionyl chloride. The 1,4-diols were synthesized from propargyl alcohol; the adduct of this alcohol and 2,3-dihydropyran, , was coupled with an aldehyde RCHO or a ketone RR′CO (R and R′ are alkyl) under Grignard conditions. The resulting products R(R′)C(OH)CCCH2OT.H.P. (T.H.P. = tetrahydropyranyl) were treated with a catalytic amount of p-toluenesulfonic acid in an excess of methanol, furnishing the diols R(R′)C(OH)CCCH2OH (R = H and R′ = alkyl or R and R′ are both alkyl) in good overall yields. Reaction of the cumulenes with equivalent amounts of alkali amide in liquid ammonia followed by hydrolysis of the reaction mixtures afforded the isomeric 3,1-enynes, R(R′)CCHCCH, in good yields. Buta-1,2,3-triene, CH2CCCH2, and hexa-1,2,3-triene, CH3CH2CHCCCH2, were isomerized by sodium methoxide in liquid ammonia to the enynes vinylacetylene, HCCCHCH2, and hex-2-en-4-yne, CH3CHCHCCCH3, respectively. In the case of buta-1,2,3-triene also a considerable quantity of the 1,4-adduct of methanol, 1-methoxy-2-butyne, CH3CCCH2OCH3, was isolated. The addition of ethanethiol to buta-1,2,3-triene and hexa-1,2,3-triene proceeded readily, yielding mixtures of isomeric adducts, C2H5SCH2CHCCH2 and C2H5SCH2CCCH3, in the first case, and C2H5CH(SC2H5)CHCCH2, C2H5CH(SC2H5)CCCH3 and C2H5SCH2CHCCHC2H5, in the second case. These compounds lost ethanethiol when treated with alkali amide in liquid ammonia, the 3,1-enynes, HCCCHCH2 and HCCCHCHC2H5, respectively, being produced.

Convenient methods for the preparation of di(1‐alkynyl) sulfides, sulfoxides and sulfones, and application of the sulfoxides and sulfones in the formation of novel heterocyclic systems

Abstract: Di(1-alkynyl) sulfides and the corresponding sulfoxides are obtained in high yields from lithium alkynides and sulfur dichloride or thionyl chloride, respectively. The di(1-alkynyl) sulfoxides and also the corresponding sulfones (prepared by oxidation of di(1-alkynyl) sulfides with m-chloroperbenzoic acid) react very rapidly with disodium sulfide, selenide or telluride to form six-membered heterocyclic compounds.

Chemistry of acetylenic ethers 104 Thermal rearrangement of 1‐alkynyl 2‐alkynyl sulfides in the presence of dialkylamines or dialkylphosphines. A new type of thio‐claisen rearrangement

Abstract: 1-Alkynyl 2-alkynyl sulfides, R1CCS-CH2CCR2, 1, rearrange at room temperature (if R2 = H) or upon heating (if R2 = alkyl). The thioketenes, H2CCC(R2)-C(R1)CS, 2, presumed to be formed can be trapped by secondary amines, or-in some cases-by dialkylphosphines. Depending upon the nature of the substituents R1 and R2 and upon the solvent, allenic thioamides, H2CCC(R2)-CH(R1)C(S)NR32, 3, conjugated dienic thioamides, H2CCHC(R2)C(R1)C(S)NR32, 4, thiophene derivatives, 5, or mixtures of these types of compounds, are formed.

Ketene thioacetals from dithioesters

Abstract: Ketene thioacetals R′CH=C(SR″) (SR′″) (with R′=H or alkyl and R″, R′″=alkyl) have been obtained in very good yields by treatment of dithioesters R′CH2C=S(SR″) with one equivalent of potassium amide in liquid ammonia and subsequent alkylation with alkyl halide R′″Br or R′″I.

Alkylthiolation of ambident anions derived from some unsaturated organic sulfides

Abstract: Reaction of the anions derived from 1,1-bis(alkylthio)-2-alkynes RCCCH(SC2H5)2 (R = alkyl, vinyl or phenyl) with dialkyl disulfides R′SSR′ or alkyl alkanethiosulfonates R′SSO2R′ gives 1,1,3-tris(alkylthio)-1,2-alkadienes RC(SR′) = C = C(SC2H5)2 in good yields. Alkylthiolation of CH3SC ≡ CC(SC2H5)2 with CH3SSCH3 affords (CH3S)2C = C = C(SC2H5)2. The 1-alkynyl sulfides C2H5C≡CSC2H5 and CH3C≡CSCH3 have been converted into CH3C(SC2H5)=C=C(SC2H5)2 and (CH3S)2C = C=C(SCH3)2, respectively by reaction with alkali metal amide in liquid ammonia and dialkyl disulfide. The latter compound dimerises on heating. Tris(alkylthio)allenes R″CH2C(SR′)=C=C(SC2H5)2 isomerise to the conjugated dienes R″CH=C(SR′)-CH=C(SC2H5)2 when heated in the presence of acids. Ethylthiolation of the anions of R′CH2C(R″)=C(SC2H5)2 (R″ = H or CH3; R′ = H, CH3 or SC2H5) gives predominantly R′CH=C(R″)-C(SC2H5)3 as isolable products.

Base-catalysed isomerization of 2-propynylamines. Synthesis of (dialkylamino)allenes

Abstract: A number of (dialkylamino)allenes 2 have been obtained in excellent yields and in a reasonable state of purity by isomerization of dialkyl-2-propynylamines 1 with potassium tert-butoxide in tetrahydrofuran or with the complex t-BuOKt-BuOH in hexamethylphosphoric triamide Treatment of the 2-propynylamines with t-BuOK in dimethyl sulfoxide leads to equilibrium mixtures of the allenic amines 2 and dialkyl-1-alkynylamines 3

Regiospecific functionalisation of unsaturated compounds via their dilithio derivatives: Part 1: Reaction of dilithio compounds of 1-alkynes with epoxides, benzyl halides and trimethylchlorosilane

Abstract: Acetylenes HCCCH2R (R = H, alkyl) have been converted with good yields into their derivatives HCCCH(E)R (E = CH2CHR′OH, CH2Ph, SiMe3) by reaction of the dilithio compound LiCCCH(Li)R with epoxides OC2H3R′ ( R′ = H, Ph), benzyl chloride and trimethylchlorosilane (TMSCI), respectivily.

Preparation of 1,3‐dienyl ethers and thioethers by alkali amide induced elimination of alcohol, phenol or thiol from 1,4‐bis‐ethers and ‐thioethers derived from 2‐butene‐1,4‐diol

Abstract: Ethers and thioethers of the type RXCH2CH=CHCH2XR (X=O or S; R=alkyl or phenyl) undergo a 1,4-elimination of RXH upon treatment with alkali amides in liquid ammonia, giving 1,3-dienyl ethers and thioethers RX-CH=CH-CH=CH2 in good or excellent yields.

Copper(I) bromide promoted reaction of grignard compounds with propiolaldehyde diethyl acetal. An efficient synthesis of allenic ethers and α,β‐ethylenic aldehydes

Abstract: Interaction between ethereal solutions of Grignard compounds RMgBr and propiolaldehyde diethyl acetal I in the presence of copper(I) bromide gives allenic ethers, III. Acid hydrolysis affords trans-α,β-ethylenic aldehydes, IV, in good to excellent yields.

Synthesis of six- and seven-membered heterocycles by reaction of 1-(2-chloroethylthio)-1-alkynes and 1-(3-chloropropylthio)-1-alkynes with alkali metal sulfide, selenide and telluride

Abstract: Reaction of RCCSCH2CH2Cl (1, R = alkyl) compounds with dilithium disulfide (Li2S2) in ethanol gives 3-alkyl-5,6-dihydro-1,4-dithiins (2, n = 2, X = S). With the alkali mono-sulfide, M2S, dehydrochlorination to (vinylthio)alkynes RCCSCHCH2 (3) predominates. Interaction between 1, n = 2, and M2Se or M2Te (M = Li or Na) in liquid ammonia gives rise to dehydrochlorination as well as to attack on chlorine with intermediate formation of alkynethiolates RCCS− (4); if this reaction is carried out in ammonia-free ethanol, the desired 5,6-dihydro-1,4-thiaselenins and -thiatellurins (2, n = 2, X = Se or Te) are, in some cases, obtained. The chloro sulfides RCCS(CH2)3Cl (1, R = alkyl or phenyl) with alkali metal sulfide, selenide and telluride yield respectively 3-alkyl- or 3-aryl-6,7-dihydro-5H-1,4-dithiepins, the corresponding 6,7-dihydro-5H-1,4-thiaselenepins and 6,7-dihydro-5H-thiatellurepins (2, n = 3). When R in the starting compounds 2 is a Me3Si group, the unsubstituted compounds 2 (n = 3, R = H) are formed.

Chemistry of acetylenic ethers 107. Synthesis of 1,4‐thiaphosphorins and 1,4‐thiarsenins

Abstract: 1,4-Thiaphosphorins and 1,4-thiarsenins (2) have been obtained by addition of phenylphosphine and phenylarsine to di-l-alkynyl sulfides under catalytic influence of lithium amide in liquid ammonia.