Isocyanates amine addition

The first route described to nonfused selenazepanes 67 from the aryl isoselenocyanates 65 and the chloro amine 66 by a stepwise amine addition-ring cyclization strategy (Equation 15) <2005TL6723> also has potential for application to the 1,3-thiazepane and 1,3-oxazepane analogues from the corresponding aryl isothiocyanates and aryl isocyanates. 

Figure 14.44 also shows how the Curtius degradation of an acyl azide can be combined with the addition of ferf-butanol to the initially obtained isocyanate. This addition gives a carbamate. In the present case a fert-butoxycarbonyl-protected amine ( Boc-protected amine ) is formed. 

Fig. 7.5. Amine addition to an isocyanate as part of the synthesis of an asymmetrical carbodiimide.

The isocyanates (9) were transformed into amino derivatives by standard reactions. Acid-sensitive aminocyclopropanes were obtained preferentially from benzyr ) -naphthyl or trifluorethyl-urethanes which were cleaved by hydrogen, EtSNa/DMF or alkaline hydrolysis. The hydrazinolysis of phthalimido compounds obtained from the urethane and phthalic anhydride also was useful Trimethylsilylethanol proved to be advantageous for the isocyanate-amine conversion the resulting urethanes gave amines upon addition of Bu4N p- 161 (e.g. synthesis of amine (21) from truns-crysanthemic acid via isocyanate (20) S equation 3). Contrarily to... 

Furthermore, tertiary amines like triethylenediamine (DABCO) are also effective catalysts for isocyanate self-addition reactions, whereas organometal-lic catalysts are generally ineffective and tin compounds are particularly poor catalysts for these reactions [10]. 

Another example of a multistep synthesis using only PSQ purification procedures was described by Hodges etal. In the first step, 1,3-diketone 47 was reacted with an excess of hydrazine 48 in the presence of morpholinomethyl-polystyrene (49). Removal of excess 48 by quenching with polymer-bound isocyanate 50 afforded pyrazole 51 with a purity of 97% (HPLC) but in quite moderate yield (48%). In the second step, 51 was converted into a mixed anhydride (by treatment with isobutyl chloroformate in the presence of 49) and subsequently transformed in situ into 5 3 by reaction with an amine. Addition of the polymer-bound reagents 50 and 52 removed excesses of chloroformate and amine by filtration and 53 was isolated in 75% yield with a purity of 97% (HPLC). 

The synthesis was initiated from 45 by displacement of the primary tosyl group with either functionalised or nonfunctionalised primary or secondary amines in NMP at 80°C to give 46. After coupling of the primary amines, the resulting secondary amines 46 were converted into ureas 47 by reaction with isocyanates or by stepwise treatment with triphosgene followed by amine addition. In addition, acyl chlorides can be employed to provide amides as exemplified for 4 9 (Scheme 4.1.10). 

Alkylation may also be brought about by an isocyanate or isothiocyanate. With strongly basic amines addition occurs (equation 19) but with less basic amines there is substitution (equation 20). In... 

Performance can be enhanced with the addition of an isocyanate crosslinker, which can lead to an overall cost reduction due to the lessened amount of crosslinker required to equal the performance of competitive urethane systems. NeoRez P-900 also features high performance and maintains excellent bond strengths under retorting conditions, which makes it ideal as a flexible packaging lamination adhesive and an alternative to commercial crosslinked, solvent-based urethanes. NeoRez P-900 is free of aromatic isocyanate and amine additives in its composition and is compliant with the U.S. Food and Drug Administration s food contact requirements. 

Keywords Additives Aliphatic Aliphatic isocyanates Amine-isocyanate reaction Aromatic isocyanates Blocked isocyanates Chain extenders Construction (application in) Glass transition temperature Hydroxyl-isocyanate reactions Hot melt reactive PU Isocyanates MDl Moisture curing PU One-component PU Packaging (application in) Plastic and composites (application in) Polyester Polyether polyols Polyisocyanates Sealants Silane PU hybrids TDI Testing of PU adhesives testing of PU sealants Testing standards TPU thermoplastic PU Transportation (application in) Two-component PU Water-borne PU... 

The intermediates in making amines are isocyanates (0==C==N) just like the Hofmann Rearrangement. The isocyanates are decomposed with water, just like the Hofmann. In fact, there is a lot of similarity between the Hofmann and the Schmidt reactions. Before I detail the synthesis steps, I should note that if you wish to generate the Hydrazoic Acid in the flask by adding Sodium Azide, you might need a powder addition funnel. This bit of equipment is quite pricey and it s likely you won t have one, so the first part of the synthesis details how to make the Hydrazoic Acid separately. 

Another type of polyol often used in the manufacture of flexible polyurethane foams contains a dispersed soHd phase of organic chemical particles (234—236). The continuous phase is one of the polyols described above for either slab or molded foam as required. The dispersed phase reacts in the polyol using an addition reaction with styrene and acrylonitrile monomers in one type or a coupling reaction with an amine such as hydrazine and isocyanate in another. The soHds content ranges from about 21% with either system to nearly 40% in the styrene—acrylonitrile system. The dispersed soHds confer increased load bearing and in the case of flexible molded foams also act as a ceU opener. 

Isocyanates are Hquids or soHds which are highly reactive and undergo addition reactions across the C=N double bond of the NCO group. Reactions with alcohols, carboxyUc acids, and amines have been widely exploited ia developiag a variety of commercial products. Cycloaddition reactions involving both the C=N and the C=0 double bond of the NCO group have been extensively studied and used for product development (1 9). 

Poly(phenylene oxide)s undergo many substitution reactions (25). Reactions involving the aromatic rings and the methyl groups of DMPPO include bromination (26), displacement of the resultant bromine with phosphoms or amines (27), lithiation (28), and maleic anhydride grafting (29). Additional reactions at the open 3-position on the ring include nitration, alkylation (30), and amidation with isocyanates (31). 

Primary cycloaUphatic amines react with phosgene to form isocyanates. Reaction of isocyanates with primary and secondary amines forms ureas. Dehydration of ureas or dehydrosulfuri2ation of thioureas results in carhodiimides. The nucleophilicity that deterrnines rapid amine reactivity with acid chlorides and isocyanates also promotes epoxide ring opening to form hydroxyalkyl- and dihydroxyalkylaniines. Michael addition to acrylonitrile yields stable cyanoethylcycloalkylarnines. 

The polyamide copolymer of dodecanoic acid with methylenedi(cyclohexylamine) (MDCHA, PACM) was sold as continuous filament yam fiber under the tradename QIANA. As late as 1981, over 145,000 t was produced using high percentages, typically 80%, of trans, trans MDCHA isomer. The low melting raffinate coproduct left after t,t isomer separation by fractional crystallisation was phosgenated to produce a Hquid aUphatic diisocyanate marketed by Du Pont as Hylene W. Upon terrnination of their QIANA commitment, Du Pont sold the urethane intermediate product rights to Mobay, who now markets the 20% trans, trans—50% cis, trans—30% cis, cis diisocyanate isomer mixture as Desmodur W. In addition to its use in polyamides and as an isocyanate precursor, methylenedi (cyclohexyl amine) is used directiy as an epoxy curative. The Hquid diamine mixture identified historically as PACM-20 is marketed as AMICURE PACM by Anchor Chemical for performance epoxies. 

AH of the amine hydrogens are replaced when MDA or PMDA reacts with epoxides to form amine based polyols. These polyols can be used in reactions with isocyanates to form urethanes or with additional epoxide to form cross-linked thermo set resins. 

In the manufacture of highly resident flexible foams and thermoset RIM elastomers, graft or polymer polyols are used. Graft polyols are dispersions of free-radical-polymerized mixtures of acrylonitrile and styrene partially grafted to a polyol. Polymer polyols are available from BASF, Dow, and Union Carbide. In situ polyaddition reaction of isocyanates with amines in a polyol substrate produces PHD (polyhamstoff dispersion) polyols, which are marketed by Bayer (21). In addition, blending of polyether polyols with diethanolamine, followed by reaction with TDI, also affords a urethane/urea dispersion. The polymer or PHD-type polyols increase the load bearing properties and stiffness of flexible foams. Interreactive dispersion polyols are also used in RIM appHcations where elastomers of high modulus, low thermal coefficient of expansion, and improved paintabiUty are needed. 

In some cases it may be desired to increase the cross-link density and hence the rigidity independently of the isocyanate-water reaction. Compounds such as glycerol, pentaerythritol and various amines have been employed as additional cross-linking agents. 

This reaction is reported to proceed at a rapid rate, with over 25% conversion in less than 0.001 s [3]. It can also proceed at very low temperatures, as in the middle of winter. Most primary substituted urea linkages, referred to as urea bonds, are more thermally stable than urethane bonds, by 20-30°C, but not in all cases. Polyamines based on aromatic amines are normally somewhat slower, especially if there are additional electron withdrawing moieties on the aromatic ring, such as chlorine or ester linkages [4]. Use of aliphatic isocyanates, such as methylene bis-4,4 -(cyclohexylisocyanate) (HnMDI), in place of MDI, has been shown to slow the gelation rate to about 60 s, with an amine chain extender present. Sterically hindered secondary amine-terminated polyols, in conjunction with certain aliphatic isocyanates, are reported to have slower gelation times, in some cases as long as 24 h [4]. 

Iodine azide, on the other hand, forms pure adducts with A -, A - and A -steroids by a mechanism analogous to that proposed for iodine isocyanate additions. Reduction of such adducts can lead to aziridines. However, most reducing agents effect elimination of the elements of iodine azide from the /mwj -diaxial adducts of the A - and A -olefins rather than reduction of the azide function to the iodo amine. Thus, this sequence appears to be of little value for the synthesis of A-, B- or C-ring aziridines. It is worthy to note that based on experience with nonsteroidal systems the application of electrophilic reducing agents such as diborane or lithium aluminum hydride-aluminum chloride may yet prove effective for the desired reduction. Lithium aluminum hydride accomplishes aziridine formation from the A -adducts, Le., 16 -azido-17a-iodoandrostanes (97) in a one-step reaction. The scope of this addition has been considerably enhanced by the recent... 

The addition of phenylisocyanate to aldehyde-derived enamines resulted in the formation of aminobutyrolactams (438,439). As aminal derivatives these produets can be hydrolyzed to the linear aldehyde amides and thus furnish a route to derivatives of the synthetically valuable malonaldehyde-acid system. With this class of reactions, a second acylation on nitrogen becomes possible and the six-membered cyclization products have been reported (440). Closely related to the reactions of enamines with isocyanates is the condensation of cyclohexanone with urea in base (441). 

In aqueous alkaline solution, the isocyanate is unstable it reacts by addition of water to give the intermediate carbaminic acid 5, which subsequently decarboxy-lates to yield the amine 3. 

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