Alkoxy isocyanates

In the absence of triethylamine, heating benzylhydroxylamine with phosgene under the same conditions, followed by the addition of 3,4-dichloroaniline, gave trichloride 160 chlorination had occurred under the reaction conditions. Furthermore, it was also found that the reactive intermediate in this process was neither an alkoxy isocyanate nor a chloroformate, but rather the allophanate 161. 

Alkoxy isocyanates are not known in their monomeric form because they undergo rapid cyclotrimerization to give the corresponding isocyanurate derivatives. ... 

Alkoxy)alkynylcarbene complexes have been shown to react with nitrones to give dihydroisoxazole derivatives [47]. Masked 1,3-dipoles such as 1,3-thia-zolium-4-olates also react with alkynylcarbene complexes to yield thiophene derivatives. The initial cycloadducts formed in this reaction are not isolated and they evolve by elimination of isocyanate to give the final products [48]. The analogous reaction with munchnones or sydnones as synthetic equivalents of... 

Chen, G. Cooks, R.G. Jha, S.K. Green, M.M. Microstructure of Alkoxy and Alkyl Substituted Isocyanate Copolymers Determined by DCI-MS. Anal. Chim. Acta 1997, 556, 149-154. 

The calculation requires measurements of the extent of reaction and of the distribution of functionality on the polymer and crosslinker. The functionality of the isocyanate crosslinker is formally three although it must be recognized that all of these materials have a distribution of functionality. Fully alkylated melamines have a functionality of 6. Coatings are formulated with an excess of alkoxy to hydroxy in order to achieve rapid cure (2). Thus, not all of the melamine alkoxy groups will react (ignoring side reactions) and the effective functionality will be less than six. 

Many organic chemicals are analyzed by RPC. These include various arylhydroxylamines as the N-hydroxyurea derivative with methyl isocyanate (614) alkyl- and alkoxy-disubstituted azoxybenzenes (6t5), n-alkyl-4-nitrophenylcarbonate esters ranging in length from methyl to octyl (616), 4-nitrophenol in the presence of 4-nitrophenyl phosphate (617), ben-zilic acid, and benactyzine-HCI using ion-pair chromatography (618), as well as aniline and its various metabolites (619), stereoisomers of 4,4 -dihydroxyhydrobenzoin (620), and aldehydes and ketones as the 2,4-dinitrophenylhydrazones (621). The technique has also been used to analyze propellants and hydrazine and 1,1-dimethylhydrazine were quantitita-vely determined (622, 623). 

This method was extensively reviewed in <84CHEC-I(4)545> and a brief summary is presented here interestingly, since the mid-1980s, this reaction has become less popular. A(-Aryl benzhydrazonyl chlorides react with thiobenzamides to form trisubstituted thiadiazolines which on treatment with alcohols furnish the 2-alkoxy derivative (Scheme 25). A-Arylbenzhydrazonyl chlorides also react with thioketenes to yield 5-methylene thiadiazolines (Equation (16)). Other examples involve the addition of the nitrileimine generated from A-trifluoroacetobenzhydrazonyl bromide to the 0=S of potassium isothiocyanate and methyl isocyanate <87JHC1391>. 

Die Herstellung von in 2-Stellung unsubstituierten4(5)-Alkoxy- bzw. 4(5)-Alkylthio-imi-dazolen ist auch aus a-Isocyan-alkansaure-nitrilen mit Alkoholen und Kaliumcarbonat als Base bzw, mit Thiolen und Triethylamin als Base moglich319,32° ... 

In einer Zweistufen-Reaktion lassen sich Oxetane in 3-Amino-alkanoIe iiberfiihren, indem man das Oxetan zunachst mit Cyan-trimethyl-silan in siedendem Dichlormethan in Gegenwart einer geringen Menge Zinkjodid umsctzt und das so erhaltene (3-Isocyan-alkoxy)-trimethy -silan mit Chlorwasserstofl -gesattigtem Methanol behandelt3. 

The dominance of an alkoxy group over a silyl group is manifested in the generation of amides from reaction of oc-silyl enol ethers with chlorosulfonyl isocyanate, followed by hydrolysis. Simple vinylsilanes and alkynylsilanes undergo carbamidation [34],... 

The Addition of Alcohols to Isocyanates AAHydro-C-alkoxy-addition... 

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). 

Another possible synthesis is offered by the reaction of alkoxy- or aryloxysulfonylisocyanate to epichloridrine derivatives. The intermediate carbamate easily cyclises upon heating in acetone <07SC2215>. Alternatively phenyl 2-hydroxyalkyl selenides can react with benzoyl isocyanate and the final carbamate cyclize after oxidation of the selenyl functionality <07SC2693>. 

The P-alkyl iminophosphoranes are considerably more reactive than the P-aryl compounds, but iminophosphoranes with alkoxy or chloro groups are also known to participate in the reaction. N-alkyl- or N-aryltrichloroiminophosphoranes are usually obtained as four membered ring dimers, which on thermolysis generate the monomers. For example, thermolysis of the dimeric N-methyltrichloroiminophosphorane 63 in o-dichlorobenzene in the presence of phenyl isocyanate affords N-methyl-N -phenylcarbodiimide 64 in 57 % yield. 

Review. New synthetic reactions based on the onium salts of aza-arenes have been reviewed (75 references). The reactions discussed involve activation of carboxylic acids or alcohols with 2-haIopyridinium, benzoxazolium, benzothiazolium, and pyridinium salts to afford 2-acyloxy or 2-alkoxy intermediates, which can be transformed into esters, amides, thiol esters, (macrocyclic) lactones, acid fluorides, olefins, allenes, carbodiimides, isocyanates, isothiocyanates, and nitriles under appropriate conditions. 

Acyloxy-l-isocyan- E14a/2, 200 (Keton/R- CO - X/AgCN) 1-Alkoxy-l-azido- EI4a/2, 117 (OR - N3), 290 (En-OSiR3 + HN3/R-OH)... 

Accordingly, uracil-/3-enamino ester, after treatment with dihalotriphe-nylphosphorane (via iminophosphorane), gives, with isocyanates in a normal kind of pyrimidine annullation (90LA901), pyrimido[4,5-pyrimidines containing a 2-alkoxy group capable of several subsequent reactions (88S919) (Scheme 56). 

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