Isocyanates synthesis from

It is also significant that patents were issued on the isocyanate synthesis from HCN (6) and a particularly interesting application would thus be available to HCN if the methods cuuld be adapted to produce an economic process. HCN already constitutes an important method for methane (natural gas) valorization, but further development can be expected in this area, for example, an important solvent such as acetonitrile can be obtained directly from CH4 and HCN. This reaction is. in fact, an interesting example of hydrocarbon activation (7],... 

Isocyanate synthesis from phosgene RNH2 + COCl 2 RNCO + HCl... 

Synthesis from OC-Amino Acids and Related Compounds. Addition of cyanates, isocyanates, and uiea derivatives to a-amino acids yields hydantoin piecuisois. This method is called the Read synthesis (2), and can be considered as the reverse of hydantoin hydrolysis. Thus the reaction of a-amino acids with alkaline cyanates affords hydantoic acids, which cyclize to hydantoins in an acidic medium. 

H-pyran synthesis from, 3, 759 bis(trimethylsiloxy) in pyrrole synthesis, 4, 333 chromene synthesis from, 3, 750 cycloaddition reactions with isocyanates, azetidin-2-ones from, 7, 261 dihydropyran synthesis from, 3, 771 fuiyl... 

The 2,3-dihydro-6/7-pyrimido[2,l-A]quinazolin-4(177)-ones 201 were obtained in a one-pot synthesis from the iminophosphorane 199 and isocyanate, through the 2-aminoquinazoline 200. Yields were good (R1 = H, Rz = c-hexyl) to excellent (R1 = Rz = Ph) (Equation 21) <1996TL9071>. 

IODOCYCLOHEXANE, 51, 45 IODODURENE, 51, 94. trans-6-Iodoisocyandtes, general synthesis from olefins with iodine isocyanate, 51, 114... 

The first publications to describe the phosphane oxide-catalyzed carbodi-imide synthesis from isocyanate appeared in 1962. In this case iminophos-phoranes were recognized as important intermediates. The first mechanistic studies also appeared at this time. Scheme 24 depicts the proposed two-step mechanism (62JA3673, 62JA4288 66CJC2793). 

Resolution of alcohols (cf., l-(naphthyl)cthyl isocyanate, 8, 356 357). A practical synthesis of the methyl ester of (S)-5-HF,TF. (1) from arachidonic acid involves chromatographic separation of the diastereomeric urethanes preparecT from the Isocyanate derived from dehydroabietylamine (hydrogen chloride and phosgene).1 Urethanes from other chiral amines are less useful. The urethanes are cleaved with triethylamine and trichlorosilanc to give the corresponding pure enantiomeric esters, which can be hydrolyzed by base. 

Eloy and Deryckere have applied their synthesis of isocarbostyrils (69HCA1755) to the preparation of thieno[2,3-c]- and thieno[3.2-c]-pyridines (Scheme 65) (70BSB301). Thermal-cyclization of 3-thienylvinyl isocyanate prepared from the corresponding azide (269) by Curtius rearrangement yields thieno[2,3-c]pyridin-7-one (270), which is transformed to (259) following usual methods. 

Synthesis from amidines, isocyanates, aldehydes and ketones 512... 

The direct synthesis of isocyanates from C02 is a challenging task, as the building up of the isocyanate group from C02 requires deoxygenation of the heterocu-mulene. A number of metal systems are capable of promoting such a transformation in their coordination sphere. 

The direct synthesis from amines and C02 (Equation 6.15) is, in principle, a more appealing route to isocyanates, if suitable methods can be developed to drive to the right this thermodynamically unfavored [61a, 119] reaction ... 

The availability of amino-substituted furazans, both by direct synthesis from aminogly-oximes and via Hofmann degradation of the corresponding carboxamides, allows urea, thiourea, imino and acylamido derivatives, for example, to be prepared by reaction with isocyanates, isothiocyanates, aldehydes and acyl halides, respectively (73JPR791, 77JCS(P1)1616). Alkoxy and acyloxy derivatives are likewise formed from hydroxyfurazans (79JHC689). 

The synthesis from silver isocyanate and phosphorus(III) chloride has proved the most dependable and gives the highest... 

In a similar context Amdtsen developed a new pyrrole synthesis from alkynes, acid chlorides either imines or isoquinolines, based on the reactivity of isocyanides (Scheme 35a) [197]. Although all atoms from the isocyanide are excluded from the final structure, its role in the reaction mechanism is crucial. The process takes place through the activation of the imine (isoquinoline) by the acid chloride to generate the reactive M-acyliminium salt, which is then attacked by the isocyanide to furnish a nitrilium ion. This cationic intermediate coordinates with the neighboring carbonyl group to form a miinchnone derivative, which undergoes a [3+2] cycloaddition followed by subsequent cycloelimination of the isocyanate unit, to afford the pentasubstituted pyrrole adducts 243 and 244 (Scheme 35a, b). 

---