Potassium unsubstituted derivatives

The unsubstituted l,3-dithiole-2-thione (245) can be accessed, however, by the reaction of dimethyl acetylenedicarboxylate with l,3-dithiolane-2-thione (Scheme 50) <74JOC2456>, from the reaction of sodium acetylide with carbon disulfide and elemental sulfur <64CB1298>, or by a two-step synthesis from the 1,2-dichloroethyl ethylether (246) and potassium trithiocarbonate. The intermediary 4-ethoxy-l,3-dithiolone-2-thione (247) affords, upon reaction with p-toluene sulfonic acid with concomitant loss of ethanol, the unsubstituted derivative (245) <76CC920>. 

Electrophilic mercuration of isoxazoles parallels that of pyridine and other azole derivatives. The reaction of 3,5-disubstituted isoxazoles with raercury(II) acetate results in a very high yield of 4-acetoxymercury derivatives which can be converted into 4-broraoisoxazoles. Thus, the reaction of 5-phenylisoxazole (64) with mercury(II) acetate gave mercuriacetate (88) (in 90% yield), which after treatment with potassium bromide and bromine gave 4-bromo-5-phenylisoxazole (89) in 65% yield. The unsubstituted isoxazole, however, is oxidized under the same reaction conditions, giving mercury(I) salts. 

Unsubstituted or alkyl-substituted 2-alkenyllithium, -sodium and -potassium derivatives are of little value in stereoselective carbonyl addition reactions. In general, these reagents exhibit high... 

All reactions of benzotriazole derivatives of the type Bt-CR RbS discussed above are based on electrophilic or nucleophilic substitutions at the ot-carbon, but radical reactions are also possible. Thus, the first report on unsubstituted carbon-centered (benzotriazol-l-yl)methyl radical 841 involves derivatives of (benzotriazol-l-yl)methyl mercaptan. 3 -(Benzotriazol-l-yl)methyl-0-ethyl xanthate 840 is readily prepared in a reaction of l-(chloromethyl)-benzotriazole with commercially available potassium 0-ethyl xanthate. Upon treatment with radical initiators (lauroyl peroxide), the C-S bond is cleaved to generate radical 841 that can be trapped by alkenes to generate new radicals 842. By taking the xanthate moiety from the starting material, radicals 842 are converted to final products 843 with regeneration of radicals 841 allowing repetition of the process (Scheme 134). Maleinimides are also satisfactorily used as radical traps in these reactions <2001H(54)301>. 

These authors found that nucleophilic additions to the unsubstituted ring system 1 can be carried out to yield a number of 7-substituted dihydro products or, in some cases, where an oxidation can follow this addition, also 7-substituted heteroaromatic derivatives (Scheme 6). Thus, reaction of 1 with indole under acidic conditions (in trifluoroacetic acid) yields 7-(177-indol-3-yl)-7,8-dihydrotetrazolo[l,5- ][l,2,4]triazine 24 <1998ZOR450>. Reaction of 1 with 3,4-difluoroacetophenone in the presence of potassium /frt-butoxide in tetrahydrofuran followed by... 

The A -unsubstituted 5-dimethylamino-l,2,4,3-triazaphosphole is converted to its anion by sodium, potassium, or their hydrides (80ZN(B)1222>. Boryl (86PS(28)7I>, silyl (80ZN(B)1222>, stannyl, phosphino, and (thio)phosphinyl <80ZN(B)1222> derivatives have been prepared mostly by reaction of the triazaphosphole with the corresponding chloride the substituents become attached to N-2. 

N-Substituted amides derived from 2-chloro- or4-chloronicotinic acid react with CH-acidic nitriles in the presence of base to yield amino derivatives of [l,6]naphthytid-5(6//)-ones and [2,7]naphthyrid-l(2//)-ones <1997JHC397>. 3-(l-Alkylamino)pyridines react with electron-deficient alkynes (acetylene dicatboxylates) in the presence of acid to give l,2-dihydro[2,7]naphthyridine-3,4-dicarboxylates in up to 72% yield compounds unsubstituted at C-1 were readily oxidized with potassium permanganate to naphthyridine-l-ones <2005TL3953>. 

Chloro, 3-bromo, 3-iodo, and 3-nitro derivatives of 5,7-dimethyl-pyrazolo[l,5-a]pyrimidine derivatives were prepared by chlorination, bromination, iodination, and nitration of 3-unsubstituted 5,7-dimethyl-pyrazolo[l,5-a]pyrimidines. Reaction with bromine and potassium thiocyanate gave a 3-thiocyanato derivative, which was converted into the mercapto derivative upon saponification. Nitrosation gives the 3-nitroso derivative and acylation with trifluoroacetic anhydride affords the trifluoroacetyl derivative (74JMC645 77JMC386). 

Dehydration procedures have led to 2//-thiopyrans. Thus unsubstituted parent heterocycle 6 was prepared by the dehydration of hydroxy derivative 287 with potassium hydrogen sulfate.20 The same procedure applied to a mixture of isomeric hydroxy 2-methyl-5,6-dihydro-2//-thiopyrans and 3,5-dihydroxy-2,4,5,6-tetrahydrothiopyran gives all the corresponding thio-pyrans.91 3-Phenylthiopyran dioxide 289 was obtained after the dehydration of hydroxy derivative 288a with phosphoric acid at elevated temperatures.300,301 The same approach was explored for the preparation of furano-2//-thiopyran 14.42... 

For example, treatment of esters 819-21 with hydrazine in refluxing ethanol gave the N-unsubstituted bicycles 9 (R1 = H). 1-Methyl derivatives (9 R1 = Me) were also prepared.22 The hydrazine 11, obtained from the acid 10a, was heated at reflux without puriiication in dilute acid to give 12 (R = H). The acid chloride 10b furnished hydrazide intermediates 10c,17,23,24 which were cyclized by fusing the solid,23 refluxing with pyridine in the presence of copper powder,24 or by heating with potassium carbonate in 1-pentanol.17... 

Triazine and some of its 3-methoxy, 3-methylthio or 3-amino derivatives (103) with the 5-position unsubstituted react with potassium cyanide to afford two products, the i-triazinyls (105) and the l,2,4-triazine-5-carboxamides (104). These are proposed to be formed via a cyanide adduct (73JHC343, 74JHC43). The bi-l,2,4-triazinyls (105) were also isolated when the triazines (103) were treated with sodium methoxide or potassium in liquid ammonia. It is suggested that the methoxide-catalyzed dimerization proceeds via an anionic intermediate (106), while the reaction with potassium in liquid ammonia occurs via a free radical process. 

Potassium cyanate, carbonic and chlorocarbonic esters, phosgene, or urea are used as cyclizing agents in the synthesis of perimidine-2-one 430 (X = X = NR, Y = O) and its derivatives from 1,8-naphthylene-diamines. Naphtho[substituted amino group in position 2 (X = Y = NH or Y = NR) are obtained on interaction of 1,8-naphthylenediamines with bromocyanogen, cyanoamide, 5-methylisothiourea, arylisothiocyanates, or dimethyltri-chloromethylamine. 

Another synthetic method for the preparation of aziridinyl ketones involves the initial modification of unsaturated ketones, with formation of /3-methoxyamino derivatives, followed by treatment with either metal alcoholates [11, 28, 29, 30, 31], or hydroxylamine hydrochloride and then potassium hydroxide [32]. An obvious drawback of this approach is the possibility of obtaining an exclusively unsubstituted nitrogen atom for the aziridinyl ketones. Among the advantages are high yields for these reactions. For example, Jin et al. [31] recorded yields of aziridine 18 of 99%. In other publications the yields of target compounds were reported to be around 90%. 

The unsubstituted nitrogen atom in 1,2,4-dithiazolidines is more prone to electrophilic reactions. Both the potassium salt 11 and the initial product 12 can participate in alkylation and acylation reactions. Alkylation of salt 11 with alkyl halides is carried out in DMF or MeCN and compound 12 can react with alkyl halides in MeCN in the presence of inorganic bases (NaH, Bu OK, AcONa, NaHCOj, CS2CO3) NaHCO( proved to be the base of choice. Yields of alkylation products 26 in some cases reach 85-90%. Compound 12 was acylated by benzoyl chloride in pyridine to form the iV-benzoyl derivative 25 (Scheme 15) <2000SL1622, 20030BC3015>. 

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