Isothiocyanates mono

Cycloaddition of 2-nitrosopyridine 48 with nitrile oxides can give either di-A -oxides such as 49 or 3-mono-A -oxides such as 50 (93JHC287). In general, greater electron withdrawing character in the aromatic substituent appears to favor formation of the di-A -oxides. Sulfur ylides such as compound 51 are obtained from aryl isothiocyanates and l-amino-2-methylthiopyridinium iodides (84JCS(P1)1891) nitrogen ylides can be obtained from a similar reaction (86H(24)3363). 

Compound 129, an intensely blue compound, was obtained by direct functionalization of DDTOMe 20b with LDA and chloro(chloromethyldimethylsilane) at one of the terminal positions followed by conversion of chloride to NCS using sodium thiocyanate in acetone (Scheme 12). The other isothiocyanates were prepared via Stille coupling of mono or dibrominated rigid cores with appropriate thienyl or phenyl stannanes followed by conversion of the chlorine atom of Si(CH3)2CH2Cl attached to a phenyl group into isothiocyanate occurred in rather low yield. 

An unusual series of nonterpenoid aliphatic isothiocyanates from a Fijian Pseudaxinyssa sp. was evident by their strong IR absorption [68]. After silica gel and reverse-phase HPLC experiments, the structures of (Z,Z)-1,18-diisothiocyanooctadeca-1,17-diene (134, n = 14), mp 15°C, and seven other di-olefinic a,mono-olefinic a, o>bisisothiocyanates (135, n = 9-18) and three a-isothiocyano-co-formyl mono-olefins (136, n = 9, 15, 16) were also identified by spectral data... 

Chip-based enantioseparations using an electrophoresis principle were presented by Gao et al. [59]. They used mono-, two-, and four-channel chips to develop chiral separations of fluorescein isothiocyanate (FlTC)-labeled basic compounds. To obtain the chiral separations, seven neutral CD were screened (i.e., a-CD, fi-CD, y-CD, HP-a-CD, HP-y-CD, and DM-fi-CD). Using the monochannel chip, the seven selectors were screened sequentially. Using the two-channel chip, between-channel repeatability could be demonstrated using the same separation conditions. Using two different selectors in the channels, the analysis time for the screening of the seven CD can be reduced to half, compared to the time needed in the monochannel... 

N-Mono- and N,N-disubstituted UREAS AND THIOUREAS, 45, 69 N-Monosubstituted thioureas from primary amines and silicon tetra-isothiocyanate, 45, 69 N-Monosubstituted ureas from primary amines and silicon tetraisocyan-ate, 45, 69... 

Subsequent epidemiological studies have supported the association between better health and long-term consumption of diets rich in foods of plant origin. " However, whether this is because such diets minimize exposure to deleterious substances (e.g., oxidized cholesterol, pyrolysis mutagens, salt, saturated fat, etc.), or maximize intake of certain beneficial nutrients (e.g., isothiocyanates and other sulfur-containing plant constituents, mono-unsaturated fatty acids, and poly-unsaturated fatty acids, PPT, poly acetylenes, selenium, terpenes, etc.) or some combination as advocated in the Polymeal concept, remains unknown. " An in vitro study indicates that there may be mechanistic basis for true synergy between PPT and isothiocyanates. ... 

In the reaction of diamines with isocyanates, the use of less than the equivalent quantities of isocyanates and isothiocyanates yields mono- and disubsti-tuted ureas and recovered diamine. The distribution of the products is dependent on the reactivity of the reagent, on concentration, and on the nature of the solvent [26] (Eq. 16). 

Insertion of unsaturated isocyanates into the M—O bond of M(OR)5 has been reported6,204,205 to give mono- to penta-substituted products (equation 4). No insertion into the Nb—O bond was observed with phenyl isothiocyanate. 

A related series of 5-substituted-2-amino-oxadiazole compounds have also been prepared in a one-pot procedure using a microwave-assisted cyclisation procedure (Scheme 6.26)164. Rapid preparation of the pre-requisite ureas from the mono acyl hydrazines and various isocyanates (or the isothiocyanate) was easily achieved by simple mixing. The resulting products were then cyclo dehydrated by one of the two procedures either by the addition of polymer-supported DMAP and tosyl chloride or alternatively with an immobilised carbodiimide and catalytic sulphonic acid. Purity in most cases was excellent after only filtration through a small plug of silica but an SCX-2 cartridge (sulphonic acid functionalised - catch and release) could be used in the cases where reactions required additional purification. 

In order to classify the reactive building blocks, we grouped them into mono-and bidentate nucleophiles (e.g. amines, alcohols, thioureas, isothioureas, amidi-nes, amidrazones), into their mono- and bis-acceptor counter parts (e.g. alkyl halides, a-bromomethyl ketones, a-alkinyl ketones), and into donor-acceptor species (e.g. isocyanates, isothiocyanates, 2-azido benzoic acids215), as depicted in Figure 40. 

Simple 1,1-enediamines react with isocyanates and isothiocyanates to afford C-acylated and C-thioacylated products, respectively. Mono- (103) and diadducts (104) can be formed when the reactant ratios are 1 1 and 1 2, respectively (equation 66)84. 

Mono- and 1,2-di-substituted alkenes react with PhSeQ/Hg(SCN)2 in benzene (0.5-96 h, at 20 C), giving -tra/if-phenylselenoalkyl isothiocyanates in 70-94% yields.2 Terminal alkenes generally give the product with the selenium terminal (an exception is the prc uct from Bu CH H2) internal alkenes show the expected stereochemistry (cis to threo, trans to erythro). Oxidation to selenoxides could be achieved cleanly only with ozone, and the products cis eliminate in the usual manner to give predominantly the vinylic isothiocyanates (Scheme 73). 

Isocyanates and isothiocyanates both react with water in a manner similar to the halosilanes to give hydrated silica. They also react with primary and secondary amines to give silylamines which, on hydrolysis, afford A-mono- and N,N-disubstituted ureas and thioureas (Scheme 31), which is a useful synthesis of these compounds. ... 

Cycloaddition of phenyl isothiocyanate (296) to pyridinium salts (295) produced imidazo[l,2-a]pyridine-2(3//)-thiones (297) (77Ml4looi). Reaction of l-aryl-2-chloropyridin-6-ones with mono-A/ -substituted ethylenediamines provided dihy-droimidazo[l,2-a]pyridin-5-ones (79CPB1207). Another procedure involves the polyphos-phoric acid cyclization of 2-(2-hydroxyethyl)aminopyridines (76AJC1039). Treatment of certain /3-aminoacrylic esters (298) with benzenediazonium fluoroborate (299) resulted in... 

Thioureas are obtained analogously by boiling an amine hydrochloride and an alkali thiocyanate in aqueous solution66 or an amine and a thioiso-cyanate in alcohol 67 aromatic thioisocyanates generally react even in the cold. Further, aqueous ammonia solutions are converted smoothly into mono-alkylthioureas by isothiocyanates.68 Isothiocyanates can be converted directly into symmetrical thioureas by boiling them in aqueous dimethylformamide or dimethyl sulfoxide the thiocarbamic acids formed as intermediates by partial hydrolysis add to unchanged isothiocyanate with loss of COS.69... 

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