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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.

Metallation of N-vinylpyrrole under presumed kinetic conditions, using n-butyllithium in THF/hexane mixtures, n-butyllithium/N,N,N′,N′-tetramethylethanediamine in hexane, or n-butyllithium/potassium tert-butoxide (1:1 molar ratio) in THF/hexane mixtures gives almost equal amounts of derivatives metallated at the α-vinyl or 2-pyrrole position. In the presence of 7–10 mol% diisopropylamine the α-vinyl-lithiated compound is transformed relatively slowly into the pyrrole-lithiated derivative at ∼ +30°c. The combined use of catalytic amounts of diisopropylamine and equivalent amounts of n-butyllithium and potassium tert-butoxide gives rise to a fast and almost complete conversion into the pyrrole-metallated derivative at temperatures in the range -60 to –80°c. A number of 2-substituted N-vinylpyrroles have been obtained in good yields by reaction with various electrophilic reagents, in most cases preceded by the addition of anhydrous lithium bromide. N-Deprotection is successful only in the case of N-vinyl-2-pyrrole-carboxaldehyde.

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.

We have found a novel and simple approach to synthesis of 2-alkyl-3-(methylthio)-5,6-dihydro-2H-2-thiopyranimines by reactions of isothiocyanates with the carbanion of methylthiobutadiene, generatedin situ when treated with the superbasic system BuLi-t-BuOK. We have established that alkylation of the synthesized thiopyrans with methyliodide in the presence oft-BuOK leads to N-alkyl-1,2-di(methylthio)-2,4-pentadiene-1-imines.

A number of derivatives of 2-imino-5,6-dihydro-2 H -thiopyran have been obtained in fair to good yields by treating the adducts from the α-metallated dienes H 2 CCHCHC(M)X (X = OCH 3 or SCH 3 ) and isothiocyanates with a calculated amount of dilute acid.

A number of 2-N-alkylamino- or 2-N-phenylamino-, 2-N, N-dialkylamino-, and 2-N-alkyl-N-phenylaminothiophenes have been prepared in good yields by adding a solution of tert-butylalcohol and potassium tert-butoxide in dimethylsulfoxide to a solution of the adduct from a lithiated 1-alkyne, RCH2C≡CLi, or the lithiated allene, tBuCH=C=CHLi, and isothiocyanate, R′N=C=S, in tetrahydrofuran and subsequently hydrolyzing the reaction mixture or quenching it with methyl iodide.

The products obtained by S -alkylation of the adducts from lithiated allenes and alkyl or aryl isothiocyanates undergo thermal rearrangements with ultimate formation of derivatives of 2,3-dihydropyridine, cyclobutanopyrroline and quinoline, depending on the structure of the isothiocyanate. In some reactions azatrienes with a fully conjugated system can be isolated.

Secondary phosphines R2PH or RR'PH (R and R' = alkyl, cycloalkyl) have been obtained in good yields by preparing lithium phosphide from lithium, red phosphorus and t-butylalcohol in liquid ammonia and subsequent alkylation in the presence of alkali amide, prepared in the same flask.

Tri(2-methoxyphenyl)phosphine has been prepared in an excellent yield by metallating methoxybenzene with n-BuLi. TMEDA in hexane and subsequently reacting the resulting lithiomethoxybenzene with phosphorus trichloride in a mixture of THF and hexane.

A number of ortho-substituted fluorobenzenes are readily accessible by treating fluorobenzene at -100°C with a 1:1 molar mixture of potassium tert-butoxide and n-butyllithium in tetrahydrofuran and hexane, and subsequently adding an electrophilic reagent.

Ethereal solutions of 1-lithiocyclohexene and 1-lithiocycloheptene have been prepared from the corresponding chlorocyeloalkenes and lithium chips in the presence of pieces of broken glass.

1,3-Diyne derivatives, (3) and related highly unsaturated compounds have been obtained with excellent overall yields by functionalization of the readily available 1-ethylthio-1,3-butenyne (1) followed by reaction of the derivatives (2) with sodamide in liquid ammonia.

Pure bromopropadiene, BrCH═C═CH2, and the corresponding iodo compound have been obtained with reasonable yields by removing the propargyl halide present in the equilibrium mixtures resulting from treatment of the propargyl halide with CuBr or CuI, with a limited amount of diethylamine.

3-Butyn-1-ol and homologues, RC°CCH2CH2OH (R=H or alkyl), have been obtained in excellent yields from alkynyllithium derivatives, RC°CLi, and epoxyethane in liquid ammonia.

1,3-Pentadiyne, HC≡CC≡C-CH3, has been prepared with yields up to 78% by reaction of methyl iodide with sodium diacetylide, prepared in situ from 1,4-dichloro-2-butyne and three equivalents of sodamide in liquid ammonia.

Secondary phosphines R2PH or RR'PH (R and R' = alkyl, cycloalkyl) have been obtained in good yields by preparing lithium phosphide from lithium, red phosphorus and t-butylalcohol in liquid ammonia and subsequent alkylation in the presence of alkali amide, prepared in the same flask.

A number of 2-alkylthiopyrroles have been obtained in fair yields by metallation of allyl isothiocyanate with a mixture of lithium diisopropylamide and potassium tert-butoxide, followed by successive addition of water and alkyl halide.

1-Alkyl-3-methoxy-2-methylthiopyrroles are obtained with high purities and in high yields by Cu(I)halide-catalyzed cyclization of the products from addition of 1-lithiomethoxyallene to alkyl isothiocyanates and subsequent methylation.

Addition of the Allenic amine H2C═C═CHNMe2 and the corresponding N-morpholinoallene to a solution of an aromatic or heteroaromatic aldehyde, RCH═O, and lithium bromide in tetrahydrofuran followed by treatment of the reaction mixture with a small amount of acetic acid at elevated temperatures affords the aldehydes RCH═C(CH2NR'2)CH═O (NR'2=NMe2 or morpholino) in reasonable yields.

Mixtures of Z- and E-1-bromo-1,3-butadiene in which the E- or Z- isomer predominates have been obtained in good yields by treating a mixture of Z- and E- 1,4-dibromo-2-butene (90% Z-isomer) or pure E-1,4-dibromo-2-butene, respectively, with powdered potassium hydroxide in high-boiling petroleum. 2-Bromo-1,3-butadiene was obtained in high yields by stirring a mixture of vinylacetylene, concentrated aqueous hydrogen bromide and copper(I) bromide.

Pure bromopropadiene, BrCH═C═CH2, and the corresponding iodo compound have been obtained with reasonable yields by removing the propargyl halide present in the equilibrium mixtures resulting from treatment of the propargyl halide with CuBr or CuI, with a limited amount of diethylamine.

1,3-Pentadiyne, HC≡CC≡C-CH3, has been prepared with yields up to 78% by reaction of methyl iodide with sodium diacetylide, prepared in situ from 1,4-dichloro-2-butyne and three equivalents of sodamide in liquid ammonia.

Trans-chloro-(2-naphthyl)-bis-(triphenylphosphine)nickel has been used to catalyze the conversion of 2-and 3-bromothiophene with alkali cyanide into the corresponding nitriles. A modified procedure for preparing the catalyst is described.

Successful O- and ortho -ring metallation of phenol and side chain metallation in o -cresol has been achieved by use of a mixture of two molar equivalents of n-butyllithium, one molar equivalent of potassium t-butoxide, and two molar equivalents of N , N , N ′, N ′-tetramethylethylene diamine in hexane. Poor results were obtained with m -cresol, thiophenol and p -cresol. m -Cresol was effectively dimetallated with a mixture of two molar equivalents of t BuOK and two molar equivalents of n BuLi·TMEDA. The effectiveness of another type of complex base based on 2-ethylhexyllithium (EhexLi) and potassium alkoxides has been also investigated, especially in respect of the influence of the concentration and the structure of the alkoxide used. With a complex base from EhexLi and 3 equivalents of potassium 3-methyl-3-pentoxide phenol was successfully dimetallated even in the absence of TMEDA. Thus, the enhanced reactivity of a complex base containing a higher concentration of a more branched potasium alkoxide over that of previously used complex bases has been confirmed.

A number of ortho-substituted fluorobenzenes are readily accessible by treating fluorobenzene at -100°C with a 1:1 molar mixture of potassium tert-butoxide and n-butyllithium in tetrahydrofuran and hexane, and subsequently adding an electrophilic reagent.

1,1′-Bis (diphenylphosphino)-ferrocene has been obtained in high (80%) yield by the reaction of l,l′-dilithio-ferrocene with chlorodiphenylphosphine.

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.

DL-1-Amino-3-buten-2-ol HH2CCH-CH(OH)-CH2NH2 has been synthesized in a satisfactory overall yield by reduction of the protected cyanohydrin H2CCH-CH(OR)-CN [R = -CH(CH3)OC2H5] with aluminum hydride, followed by removal of the protecting group with aqueous hydrochloric acid and treatment with potassium hydroxide. The amino alcohol is a key intermediate in a synthesis of the antithyroid factor goitrin reported previously.

Reaction of dimethyl sulfoxide with two equivalents of lithium in liquid ammonia gives a solution of lithium methanesulfenate which can be alkylated or benzylated to yield the corresponding sulfoxide.

3-Butyn-1-ol and homologues, RC°CCH2CH2OH (R=H or alkyl), have been obtained in excellent yields from alkynyllithium derivatives, RC°CLi, and epoxyethane in liquid ammonia.

Ethereal solutions of 1-lithiocyclohexene and 1-lithiocycloheptene have been prepared from the corresponding chlorocyeloalkenes and lithium chips in the presence of pieces of broken glass.

1-Amino-2-propyne has been obtained in good yields by successive solvolysis of propargyl bromide in liquid ammonia, metalation of the dissolved amine with sodamide, and hydrolysis after complete removal of the ammonia by evaporation. Some homologues, RC≡CCH 2 NH 2 , have been obtained in fair yields by addition of alkyl bromides to the solution of the sodium derivative of 1-amino-2-propyne.

Reinvestigation of the recently published formation of silylated alkynes by reaction of 1-alkynes with zinc and trimethylchlorosilane in acetonitrile showed that appreciable amounts of 1-alkenes are formed as side products.

Recently1 we reported excellent preparative methods for 2-bromothiophene involving addition of hydrogen peroxide to a mixture of concentrated aqueous hydrogen bromide, thiophene and diethyl ether or addition of a solution of bromine in concentrated aqueous hydrogen bromide to a mixture of thiophen, diethyl ether and aqueous hydrogen bromide. Similar procedures with furan gave intractable mixtures of unindentified products. A literature search afforded only two procedures2,3 for the direct bromination of furan, viz. the reactions of furan with hexabromocyclopentadiene and the bromine-dioxan complex. Although good yields are reported, these methods do not seem attractive for the preparation of 2-bromofuran in sizable amounts. We have applied the well-established reaction of lithium compounds with elemental bromine to prepare 2-bromofuran.

1-Alkyl-3-methoxy-2-methylthiopyrroles are obtained with high purities and in high yields by Cu(I)halide-catalyzed cyclization of the products from addition of 1-lithiomethoxyallene to alkyl isothiocyanates and subsequent methylation.

A number of 2-alkylthiopyrroles have been obtained in fair yields by metallation of allyl isothiocyanate with a mixture of lithium diisopropylamide and potassium tert-butoxide, followed by successive addition of water and alkyl halide.