Quinolines isothiocyanates

Formate esters behave as typical carbonyl compounds in reactions with a number of ylides, eliminating phosphine oxide and forming vinyl ethers, e.g. (33).35 Stabilized phosphoranes are able to condense with the carbonyl group of cyclic thioanhydrides (34).38 Quinoline derivatives, e.g. (35), are obtained from the condensation of dicar-boalkoxy-ylides with isocyanates.37 Benzoyl isothiocyanates and keto-phosphoranes give quantitative yields of (36), which are unreactive in Wittig reactions but can be readily oxidized by selenous acid.38 The products obtained from reactions (Scheme 9) with the triazolinedione (37) depend upon the stability of the ylide used.39... 

Although marine organisms produce a large number of isocyanates, isothiocyanates, and formamides, the corresponding thiocyanates have rarely been encountered. Indeed, the thiocyanate functionality has only been found in six sesquiterpenes (263-268), in four tricyclic quinoline alkaloids (271-274), and in psamaplin B (172) (included in the bromotyrosine derivatives discussed in the disulfide/polysulfide section). They have been found in marine sponges, as well as in nudibranches and tunicates. 

The schemes presented below also illustrate the synthesis of various amides of substituted quinoline-and quinolonecarboxylic acids 212-214 by the reaction of isatins 7, 9, 54, and 180 with amides 215 [179], acylated amino acids 216 and isothiocyanates [182], and enamines 217 [183],... 

SAR studies were performed on compoimds containing the 9H-isothia-zolo[5,4-fc]quinoline-3,4-dione (ITQ) nucleus and it was found that some of them are potent antibacterial agents (see Scheme 101) [114,115]. They were prepared from compound 353, which was treated with cyclopropyl isothiocyanate in DMF and then with Mel. Compound 354 (94%) was obtained and treated with in NaH in DMF to give the isothiazolo[ 5,4-fo] quinoline compound 355 (93%). Its treatment with anhydrous NaSH gave the corresponding mercaptan (84%), which was directly cychsed without purification to 356 (85%) in the presence of hydroxylamine-O-sulfonic acid. Microwave-assisted Suzuki-Miyaura cross-coupling of the ITQ nucleus 356 with the desired aryl-boronic esters or acids afforded derivatives 357, typically, in 30-50% yield after HPLC purification (Scheme 87). 

AllenylHthium compounds can function as nucleophiles for the synthesis of quinolines. The reaction of 3-methyl-1,2-butadienyllithium with phenyl isothiocyanate in THF at -70 C produces the allenyl thio-carboximidate, which can be thermally cyclized to 2-methylthioquinoline (Scheme 14). ... 

Pyrimido[4,5-fr]quinolines 344 were obtained from 2-amino-3-cyanoqui-noline 280 (R = Ar1) upon reaction with benzoyl isothiocyanate (96IJC(B)608) (Scheme 67). Reaction of enamine 31 (R = o-CNC6H4) with benzylidene malononitrile in the presence of DBU gave the pyrimidoquinoline 345 via the respective quinoline 280 (01ARK73). A series of pyrimidoquinolines were prepared by cyclization of the... 

Derivatives of (6) and its 6,7- and 4,4u,5-benzologues were prepared from 2-(2-hyd-roxyethyl)piperidine with isothiocyanates <76UC(B)770>, from 3-(2-hydroxyethyl)-l,2,3,4-tetra-hydroisoquinoline with CS2 <79GEP2848926>, and from 8-hydroxymethyl-1,2,3,4-tetrahydro-quinolines with CS2 or COS <87EUP239927>. Derivatives of (6) were also obtained in the reaction of 2-(2-haloethyl)piperidines with thiourea <7073941,82OMR(20)239>, and CS2 <63JOC98l>. 

Treatment of N-2,4-dinitrophenylpyridinium chloride (778) with phenyl-hydrazine in acetic acid causes reductive cyclization to yield the pyrido[l,2-ajimidazole (779). 3-Aminocrotononitrile, MeC(NH2)=CHCN, condenses with quinoline 1-oxide and isoquinoline 2-oxide to form the tricyclic compounds (780) and (781), respectively." The imidazo[5,l-a]isoquinoline derivative (783) is obtained by the action of phenyl isothiocyanate on the sodium salt of the Reissert compound (782)." ° Triethyl phosphite reduces the o-nitrophenyldipyr-rolylmethane (784 R=N02) to the nitrene (784 R = N), which forms the pyrrolo[3,2-6]quinoline derivative (785) by an intramolecular insertion reac-tion." 3-Amino-177-isoindole (786) reacts with acetylacetone in the presence of perchloric acid to yield the pyrimidoisoindolium salt (787). ... 

The infrared spectra of a number of complexes of metals with pyridine and quinoline (Frank and Rogers, 1966) and with isothiocyanate (Clark and Williams, 1966) have been reported. Infrared data have been given for metal—leucine chelates (Jackovitz and Walter, 1966). 

Preparation of Isothiocyanates. Ethoxycarbonyl isothiocyanate (18), useful as a synthetic reagent for heterocyclic syntheses, can be prepared in excellent yield from the reaction of ethyl chloroformate (16) with sodium thiocyanate (17) using quinoline as a base catalyst (eq 9). Only trace amounts of the isomeric thiocyanates are formed in the reaction. In the absence of the base catalyst, only a moderate (65%) yield of the desired product is obtained, along with significant (10%) contamination by the isomeric ethoxycarbonyl thiocyanate. Pyridine can also be used as the catalyst here however, it reacts faster, which sometimes leads to undesired byproduct formation. 

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