Hydrazines with isocyanates

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. 

Hydrazines react with isocyanates to give either 1,4- or 2,4-disubstituted semicarbazides (see Scheme 1). Alkylhydrazines react in a similar fashion to produce only the 2,4-dialkylsemicarbazides [41, 42] (Eq. 13). 

In Scheme 1 the most useful laboratory method for the preparation of semicarbazides involves the reaction of hydrazines with ureas or isocyanate derivatives (organic and inorganic). 

Examples of the reaction of substituted hydrazines with aryl or alkyl isocyanates are given in Table VI. 

Reaction of Substituted Hydrazines with Alkyl or Aryl Isocyanates... 

Functionalization of Ni(MeCOCHCOMe)2 occurs in reactions with isocyanates, diethyl azodi-carboxylate and dimethyl acetylenedicarboxylate, which proceed by formal insertion of the methine C—H unit into the substrate multiple bonds to form respectively amides and ester-substituted hydrazines and alkenes. Similar additions of acetylacetone to these electrophiles is catalyzed by nickel acetylacetonate.217,218... 

A robust catch, cyclize, and release preparation of 3-thioalkyl-1,2,4-triazoles mediated by the polymer-bound base P-BEMP has been described <02TL5305>. Reaction of solid-supported hydrazides 103 with isocyanates or isothiocyanates followed by base-induced cyclization/cleavage afforded 1,2,4-trisubstituted urazoles and thiourazoles 104 <02JCO491, 02TL3899>. Polymer-supported V-acyl-1 //-benzotriazole- 1-carboximidamides 105 reacted with hydrazines followed by acidic cyclizative release to give 3-alkylamino-l,2,4-triazoles 106 <02OL1751>. 

In an approach combining step growth polymerization with ring opening polymerization, Uchida and coworkers prepared a linear polyurethane capped with isocyanate groups on both ends [40]. This macromonomer was then mixed with NCA and hydrazine initiator, which was designed to... 

Satyanarayana et al. (2006) used EC, ABS, and hydrophobic modified EC man-branes (dense) for hydrazine-water system PV. Hydrophobic modified ethylceUulose membrane (ECNCO) was prepared by reacting ethylceUulose with isocyanate. These membranes were used in the PV of a hydrazine-water system. Both are highly polar liquids. The results are given in Table 9.2. The PV flux through the EC membrane is somewhat larger compared with ECNCO and ABS. These data were correlated with... 

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