Alicyclic isocyanates

Figure 3.39 Alicyclic isocyanates, (a) Isophorone diisocyanate (or 3-isocyanato-methyl-3,5,5—trimethylcyclohexyl isocyanate), Huels IPDI (b) l,4-bis(isocyanatometh-yl)cyclohexane, Mobay s p-Desmodur (c) l,3-bis(isocyanatomethyl)cyclohexane, Takeda s Hr,XDI (S3.50) (d) Methylene bis(4—cyclohexylisocyanate), Mobay s Desmodur W ( 3.00). also known as H12MDI, RMDI (reduced MD1), and PACM [bis-/ -aminocyclohcxyl methane].

Alcohols, reaction of isocyanates with, 224-225 Alcoholysis, 69 Alicyclic dianhydrides, 297 Alignment coating, for liquid crystal devices, 269-270 Aliphatic AA-BB-type polyamides, synthesis of, 164-173 Aliphatic AB-type polyamides, 173-180 Aliphatic acids, 60... 

Glyphosate diarylphosphonate nitriles 31 reacted with aryl isocyanates to form the corresponding alicyclic ureas 102, which were thermally quite labile and easily reverted back... 

The palladium-phosphine-catalyzed cycloaddition reactions of vinyloxetanes 530 with aryl isocyanates or diaryl-carbodiimides led to 4-vinyl-l,3-oxazin-2-ones 531 or l,3-oxazin-2-imines 532, respectively (Scheme 101). In the absence of phosphine ligands (PPhs, bis(diphenylphosphino)ethane (DPPE), l,3-bis(diphenylphosphino)propane (dppp), no conversion of heterocumulenes was observed. Starting from fused-bicyclic vinyloxetanes, both types of cycloadditions proceeded in a highly stereoselective fashion, affording only the r-isomers of alicycle-condensed 1,3-oxazine derivatives <1999JOC4152>. 

The 1,2-dipolar cycloaddition of chlorosulfonyl isocyanate to different cycloalkenes has become a well-known route for the synthesis of cycloalkane-fused p-lactams, and for alicyclic P-amino acids, after hydrochloric acid treatment. The addition takes places regio- and stereospecifically, in accordance with the Markovnikov orientation rule [51-55]. In this manner, a number of homologue and analogue alicyclic P amino acids have been prepared, such as czs-2-amino-2-methylcyclopentanecarboxylic acid [56], m-2-amino-2-methylcyclo-hexanecarboxylic acid [56], (l/ , 2S, 4S )2-amino-4-terMnitylcyclopenta-necarboxylic acid [55, 58], 3-exo-aminobicyclo[2.2.1]heptane-2-exo-carboxylic acid [59, 60] and 3-exo-aminobicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid [61]. 

Other electrophiles, such as aromatic and aliphatic aldehydes, alicyclic ketones, or isocyanates, were also used successfully in 1. the second step giving rise to unsymmetrical a-hydroxy ketones 2. and a-keto amides after hydrolysis. Attempts to utilize an ester carbonyl group as an electrophile, however, failed the reactions 3. were low-yielding, and the expected products were accompanied 4. by a number of byproducts. 

Carbamate esters also react with BCI3 in the presence of EtjN to afford isocyanates under mild reaction conditions (Schane 23.13)." In most cases, quantitative or near-quantitative conversion to isocyanates is achieved in aryl, alkyl, alicyclic, and tosyl carbamate esters. 

Unfortunately, the aromatic isocyanate component in a PU chain may contribute to poor oxidative resistance, particularly under UV-radiation. Employing mixtures of stabilizers has limited success in eliminating embrittlement or yellowing. Alicyclic and aliphatic isocyanates give good resistance to UV, (e.g. isophorone diisocyanate), finding use in products for exterior applications (e.g. surface coatings) but are more than five times as expensive and tend to be less reactive than the aromatic types. 

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