Isocyanates formamides

Nitrogen trifluoride Difluoramine Nitrous acid Nitric acid Cyano fluoride Formyl fluoride Carbonyl fluoride Acetyl fluoride Acetyl cyanide Isocyanic acid Methyl isocyanate Formamide Nitromethane Nitrobenzene... 

Isocyanates have been catalytically hydrogenated to N-substituted formamides RNCO —> R—NH—Isothiocyanates were reduced to thioformamides with Sml2 in HMPA/t-BuOH. ... 

Elastomeric fibres based upon both polyester-urethane and polyether-urethane structures followed. The early work by Bayer led to the use of highly polar solvents such as dimethyl formamide. Formation of fibres by reactive spinning, where the isocyanate-ended polymer is extruded into an aqueous solution of a chain-coupling agent, was described in 1949 [75] and by dry-spinning a solution of the chain-coupled polymer in 1951 [76], However, Bayer did not immediately use their technology to produce commercial fibres [77],... 

Reactions involving the [4 + 1 + 1] principle, an example of which is shown in equation (136), are rather uncommon and of strictly limited utility [3 + 2 + 1] and [2 + 2 + 2] processes, on th,e other hand, are well known. Representative [3 + 2+1] three-bond formation processes are given in equations (137)—(141), from which it can be seen that the common situation is where ammonia, a substituted amine or formamide constitutes the one-atom fragment. Many [2 + 2 + 2] atom fragment syntheses are known and some are familiar reactions. Thus, the cobalt(I)-catalyzed condensation of nitriles and isocyanates with alkynes gives pyridines and 2-pyridones, often in excellent yield (e.g. equation 142), while the cyclotrimerizations of nitriles, imidates, isocyanates, etc., are well established procedures for the synthesis of 1,3,5-triazine derivatives (e.g. equation 143). Further representative examples are given in equations (144)-(147), and the reader is referred to the monograph chapters for full discussion of these and other [2 + 2 + 2] processes. Examination of the... 

Isocyanates have been catalytically hydrogenated to N-substituted formamides RNCO R—NH—CHO.332... 

Diterpene isothiocyanates fall into three distinct structural categories regarding their carbon skeletons the acyclic tetraenes (220 and 221), the biflorane framework (including the kalihinol family) (222-238), and the amphilectane framework (including the cyclo- and isocycloamphilectanes) (239-241). Like the sesquiterpene isothiocyanates, most of these compounds were isolated along with the corresponding isocyanate and formamide compounds. 

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. 

Cope and Burrows414 have prepared a number of aminoalkylbenzo-[6]thiophenes with the general formula (195) by Friedel-Crafts reaction between benzo[6]thiophene and various amino tertiary alcohols. On treatment with formamide in formic acid, (3-benzo[6]-thienyl)acetone affords 3-(2-aminopropyl)benzo[6]thiophene [Eq. (11)].557 Recent patents535,570 describe how isocyanates with the... 

Dealkylation of tertiary amines with dibenzoyl peroxide, 44, 74 Decarboxylation, intermolecular, of isocyanates to carbodiimides, 43,32 Decker synthesis of amines, 44, 7t, 75 Dehalogenation of l,l,2-trichloro-2,3,3-trifluorocydobutane, 42,45 Dehydration, of formamides with phosphorus oxychloride to isocy-anides, 41, 13, 101 of 4- 2-hydroxyethyl)piperidine to quinuclidine, 44, 90 Dehydrohalogenation of 2-chloroallyl-amines to propargylamines, 44,55 Delepine reaction, to prepare 2-bromo-allylamine, 43, 6 Deoxyanisoin, 40,16 Deoxybenzoin, 40, IT Deoxypiperoin, 40, IT Deaylamine, 41, 8T... 

The reaction of isocyanates and isothiocyanates with 3(5)-aminopyrazole-4-carbonitrile affords aminopyrazolo[3,4-d]pyrimidines <90CCC728,91TL6787). Intermediate pyrazolyl thioureas were isolated in several cases and cyclized into aminopyrazolo[3,4-. The reaction of the amines (315) with formamide gives aminopyrazolo[3,4-t/]pyrimidines <8lOPP379>. 

Hydrogenation of isocyanates using 10% palladium-on-carbon catalyst has also been used to prepare N-alkyl formamides (3). 

A few other A-substituted imines have occasionally been reduced to amine derivatives. Thus, A(-nitro imines (nitrimines) are reduced by NaBH4/dioxane %tOH/AcOH to A -nitroamines (Table 16, entry 14), and nitronate salts are reduced by BH3/THF to hydroxylamines (entry 15) via oximes. Isocyanates are reduced by LiBHEts, LiAlH(OBu )3 (at low temperature), or PhsSnH to formamides, which may be hydrolyzed in acidic workup to amines,while reduction with LAH affords A/-methylamines. ... 

Imidazoles have been N-acylated by isocyanates (at elevated tempera-tures) " (Scheme 21), acid halides, and alkyl chlorocarbonates, but 2-methylimidazole would not react with formamide and phosphoryl chloride. Trifluoromethylsulfonation forms the imidazolide which is a convenient reagent for the introduction of the triflate group. ° With highly basic I-substituted imidazoles, acetyl halides form the 1-acetyl-... 

Another interesting bromide ion-catalyzed reaction is the anodic oxidation (undivided cell) of secondary formamides in methanol leading to urethanes [232]. This reaction proceeds via the intermediate A-bromo amide, which under elimination of HBr forms the isocyanate, which is attacked by methanol. Thus, a phosgene-free technical synthesis of urethanes is made possible. Urethanes can be used as stable isocyanate equivalents [Eq. (42)]. 

The addition of isocyanates to glycals, which has been studied thoroughly in connection with new methods of synthesizing lactams [256], usually affords a mixture of [2+2] and [4+2] cycloadducts. These primary reaction products are rather unstable and slowly rearrange to unsaturated amides, which can often be isolated directly from reaction mixtures [257,258]. In the case of simple dihydropyran derivatives 168, unsaturated A-substituted C-2 formamides 170 are the only isolable products (O Scheme 57) [259,260]. 

In either dimethyl-formamide or dimethyl sulfoxide, the reaction rates became too fast to measure even in the absence of a catalyst. It thus appears that while the ionizing power of the solvent as indicated by the dielectric constant is an important factor for the solvent effect, it is not the only one. The slow reaction in the case of acetonitrile may have been caused by the nitrile competing with the isocyanate for the electrons of the base catalyst and thereby neutralizing the catalyst by complexing. 

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