Bonding, isocyanate, chemistry

From the perspective of macromolecular science and especially for the isocyanate chemistry, the main problem resides in the elucidation of the hydrogen bond associates structure especially in the case of diols and polyols as in fact they finally represent the products involved directly in the macromolecular synthesis. Certainly a similar question is also risen in the case of diamines leading to the urea groups formation. 

Oxaziridines 381 have been reacted with chlorosulfonyl isocyanate (Scheme 65), this time forming 1,2,4-oxadiazolidin-3-ones 382 via C-N bond cleavage. The structure of the product was established by X-ray crystallography as the 3-one rather than the 5-one that might be expected on the basis of the chemistry shown in... 

The Chemistry of N-C02 Bonds Synthesis of Carbamic Acids and Their Derivatives, Isocyanates, and Ureas... 

A review of the chemistry and biological actions of colchicine and its derivatives has been published.536 The 13C n.m.r. spectra of colchicine and its derivatives have been studied537-540 and the structure (119) has been determined for epoxycolchicine (prepared from colchicine by the action of water and sodium peroxide) by X-ray crystallographic methods 541 other n.m.r. studies have shown that the double-bond in dehydro-7-deacetamidocolchicine is placed as shown in (120), and not in the 6,7-position, as previously supposed.542 The treatment of deacetyl-colchicine with isocyanates affords the related substituted ureas, which can be converted into A-nitroso-derivatives by treatment with nitrous acid these have been evaluated as inhibitors of neoplasms and as virucides.543 /V-Demethylation and O-demethylation of A-methylcolchiceinamide by micro-organisms has been achieved.544... 

Some of the more interesting and innovative work has occurred in areas combining aspects of more than one chemistry type. For instance, moisture-curable thermoplastic adhesives have received much attention. Hot melt adhesives have been developed that contain active, moisture-curable isocyanate groups. The compositions provide rapid processing on assembly lines because a reasonable bond is formed as soon as the thermoplastic adhesive cools from the melt. However, bond strength and performance improve with time as the composition is slowly crosslinked to a thermoset by reaction of the isocyanates with atmospheric moisture.96,97... 

The crystal stmcture revealed the pyramidal geometry around lead atom with two unequal Pb-N bonds of2.344(7) A and 2.372(6) A. Similar chemistry was observed with aryl isocyanates. 

The uranium-carbon multiple bond has an extensive insertion chemistry with polar unsaturated molecules including carbon monoxide, nitriles, isocyanides,and isocyanates. Metal carbonyls also insert into this bond to form metallaphosphoniumenolates, which undergo novel reactions... 

There is a rich chemistry of the addition of OH and SH bonds to organic cyanates, isocyanates, and thiocyanates... 

The year has seen a considerable extension of the principles of hypervalent phosphorus chemistry into the fields of other elements notably Si, Sn, Ge and Sb and in this context the well-known Martin ligand has proved to be especially valuable. Particularly interesting contributions have been provided by Ju et al on the relative rates of reaction of pentoses and hexoses with pentacoordinate phosphorus, by Bentrude et on the mechanism of the reaction of hy-dridophosphoranes with dimethyl disulfide and by Kawashima et alP on the isolation of two carbaphosphatranes containing covalent P-C bonds. Holmes et al report on the fluxional properties of propeller shaped phosphoranes and Buono et have also demonstrated the utility of hydridophosphoranes in some highly diastereoselective reactions with isocyanates. In summary, although the number of reports was small, the year was noteworthy for some very sophisticated contributions to the field. 

The predominant structure in these resins is the isocyanurate linkage. These are relatively stable and it is the chemistry of the residual isocyanate groups that dominate the formation of new bonds in the system during the... 

Synthesis of (5,5) systems via a (3 - - 2) approach is essentially based on 1,3-dipolar cycloaddition chemistry. Cyclic nitrones (e.g., (80)) react with phenyl isocyanates <74H(2)297, 76JA1478> and phenyl isothiocyanates <72TL4i9i, 73AJC2473> to form oxadiazolidines (81) by addition of the dipole exclusively to the C=N bond. However, with substituted phenyl isothiocyanates, dipolar cycloaddition... 

Pentafluoro(isocyanato)-A -sulfane is a convenient starting material for the syntheses of compounds containing the SF5Nwith carboxylic acids, alcohols, aldehydes, amines, and compounds with acidic C-H bonds have been studied. In these cases, the chemistry of the isocyanate group follows expected reaction paths. The reactions of SF5NCO with silylated nucleophiles have produced a more diverse chemistry. Recently, the isocyanate has been used to incorporate SFs... 

The first examples of the 1,3-oxazete system (44) have been prepared by the sequence shown in Scheme 8. The first stable 4-imino-l,2-oxazetidines (45) have been obtained from [3 + 1] cycloaddition of isocyanides to N-neopent-ylidene-t-butylamine AT-oxide. Their chemistry is dominated by O—N bond cleavage for example, acid brings about rearrangement to amino-acid derivatives, and, in the presence of tetrahydroisoquinoline, cyclo-reversion to give imine and isocyanate can be detected. An unstable 1,3-oxazetidine is involved in the reaction of the imine (46) with the aldehyde (47) to give the imine (48). ... 

Schematic illustration of functionalization of a glass substrate by HMDIC followed by immobilization of the 11-HUDA surface-modified CdSe nanoparticles on the isocyanate-bearing substrate through the carbamate-bond forming reaction. Dalton Transactions, 43, 9426 (2009). Reproduced by permission ofThe Royal Society of Chemistry. 

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