Nucleophilic reactions of 1-substituted-2,5-dithiobiureas with chloronated benzo-and naphthoquinones as well as (1,3-dioxo-2,3-dihydro-1( H )-inden-2-ylidene)propanedinitrile

Nucleophilic attack by 1-substituted-2,5-dithiobiureas on C-2, C-3 of 2,3,5,6-tetrachloro-1,4-benzoquinone and 2,3-dichloro-1,4-naphthoquinone initiates the formation of benzo-and naphthoimidazothiadiazolediones. On the other hand, 1-substituted-2,5-dithiobiureas attack 2,3,5,6-tetrachloro-1,4-benzoquinone and 2,3-dichloro-1,4-naphthoquinone at (C-1, C-2, C-4 and C-5) as well as (C-1, C-2, C-3 and C-4), respectively to form benzo-and naphthoimidazothiadiazoles. The reaction of (1,3-dioxo-2,3-dihydro-1( H )-indene-2-ylidene)- propanedinitrile with 1-substituted-2,5-dithiobiureas forming the derivatives of (oxoindeno-thiazinylidene)hydrazinecarbothioamide as well as (oxoindenopyrrolylidene)hydrazinecarbo-thioamides. A rationale for the conversions observed is presented.

A rationale for the formation of products 9a-c and 10a-c.
Compounds 16a-c were obtained as characteristically reddish brown colour crystals.For example 16c, its molecular structure is supported by the following findings: The gross formula C 20 H 16 N 8 S 2 represents product from one molecule of dichloronaphthoquinone (7) and two molecules of 6c with loss two molecules of HCl and another two of H 2 O.The low-field NHattached to allyl group is present with the aromatic protons, in addition to allyl and aryl protons.In 13 C-NMR spectrum, (C-12a, C-14a) and (C-2, C-11), resonate at δ = 152.56 and 159.63 ppm, respectively.The presence of allyl group is also evident from 13 C-DEPT-NMR spectrum exhibiting positive signal at δ = 135.12(allyl-CH=) and negative signals at 42.96 and 114.88 due to (allyl-CH 2 N) and (allyl-CH 2 =), respectively.The EI mass spectrum of 16c is characterized by molecular ion of low intensity and the loss of 198 a.m.u (representing two molecules of allylisothiocyanate).The resulting fragment ions undergo loss of 30 a.m.u (most likely dinitrogen and hydrogen molecules) followed by the appearance of allyl cation as a base peak at 41. Scheme 3. New products formed during the reaction of 1-substituted dithiobiureas 6a-c with 2,3dichloronaphthoquinone (7).
The structures of 17-19 have assigned on the basis of their IR and NMR spectral data.The gross compositions of 17-19 were derived from satisfactory elemental analyses and the molecular masses.The IR spectra of all compounds showed sharp band due to cyano group at 2220-2210 cm -1 , NH absorptions at 3340-3240 cm -1 .3][34][35] The 1 H-NMR spectrum of (C=S) and 195.12 (CO).The structure of 18b was evidently confirmed by mass spectrometrically.Besides the molecular ion at m/z = 403 (22 %), the characteristic fragment ion pattern of benzylisothiocyanate at 149 (47), benzoyl group at 105 (81) and benzyl cation at 91 as a base peak.
A minor product (7-11 %) from the reaction between 6a-c and 8 contains N-substituted (oxoindenopyrrolylidene)hydrazinecarbothioamides 19a-c.As an example, the structural assignment of 19c was supported by the following spectral data.In its 13 C-NMR spectrum, the characteristic resonance signal of the carbonyl carbon atom of indandione 8 appeared at δ = 194.83ppm. 36Signals at 121.23, 158.31, 145.92 and 152.29 due to (C-3), (C-2), (C-3a) and (C-8b), respectively.The 1 H-NMR in DMSO-d 6 of 19c displayed broadened signals at δ = 4.12 (allyl-CH 2 N), 7.79 (allyl-NH) and 9.77 (hydrazine-NH) as well as multiplets at 5.14-5.17(allyl-CH 2 =), 5.90-94 (allyl-CH=) and aromatic protons.The presence of allyl group is also evident from 13 C-DEPT-NMR spectrum which exhibits negative signals at δ = 42.83(allyl-CH 2 N) and 118.41 (allyl-CH 2 =) as well as positive signal at 135.16 ppm due to (allyl-CH=).The elemental analysis supported the gross composition C 16 H 11 N 5 OS and the mass spectrum revealed the expected molecular ion.The formation of structure products 17-19 may be rationalized as in Scheme 6.Two routes can be suggested for the formation of cyanomethyleneindanedione 20.The first, is abstraction of a proton from 6a-c by the carbanione 8-H˙¯ to give (1,3dihydroxyindan-2-ylidene)propanedinitrile 21 which loss a molecules of HCN to form 20. In second route, cyanide ion released from the anion 8-H˙¯. 30Combination of 6a-c and 20 with the elimination of H 2 S and H 2 O afforded the substituted (oxoindenopyrrolylidene)hydrazinecarbothioamide 19.Also, compound 19 may be formed via the formation of 22 as an intermediate.Several alternative structures based on the same elemental composition could be eliminated according to previous 1 H-NMR and 13 C-NMR spectral data.
A rationale for the formation of products 17-19.
On the other hand, the reaction of 6a-c with 2,3-dicyano-1,4-naphthoquinone in ethyl acetate (under our reaction conditions reported with compound 8) afforded the thiadiazoles 12a-c and dihydrodicyanonaphthoquinone.

Experimental Section
General Procedures.Mps have been determined using open glass capillaries on a Gallenkamp melting point apparatus and are uncorrected.The IR spectra were recorded with a Shimadzu 408 instrument using potassium bromide pellets.The 1 H-NMR (400.134MHz) and 13 C-NMR (100.6 MHz) spectra were measured in DMSO-d 6 using a Bruker AM 400 with TMS as an internal standard.Assignments of carbon resonances have been supported by DEPT experiments.Mass spectra have been obtained with a Varian MAT 311 instrument using electron impact ionization (70 eV).Elemental analyses have been determined by the Microanalytical Center, Cairo University, Egypt.Preparative layer chromatography (plc): Glass plates (48 cm x 20 cm) were coated with silica gel Merck Pf 254 (applied as aqueous slurry and air-dried affording a 1mm layer).Zones were detected by indicator fluorescence quenching upon 245 nm illuminations, removed from plates and extracted with acetone.

Reaction of 2a with 1-substituted-2,5-dithiobiureas 6a-c
A solution dithiobiureas 6a-c (1.0 mmole) in 15 ml of dry tetrahydrofuran (THF) was added dropwise to a solution of 2a (2.0 mmole) in 25 ml of dry THF at room temperature.The reaction mixture becomes deeply blue or purple colour.It was left standing for 48 hours, filtered and the precipitate was washed several times with THF and identified as disubstituted benzo [2,3- 3,4]-thiadiazoles) 10a-c.The filtrate was concentrated in vacuum and the residue separated by plc using toluene/ethyl acetate (10:1) to give only one zone which was removed and extracted to give substituted benzo [4,5]