Phenyl isocyanate insertion reactions

Organocopper compounds react slowly with nitriles or not at all 124, 233). Only a low yield of benzanilide was obtained from the reaction between phenylcopper and phenyl isocyanate 124). Isocyanate insertion reactions with vinylcopper compounds in HMPT in the presence of P(0C2H5)3 afford acrylamides 225a). 

The reactivities of hydrido(phenoxo) complexes of trons-[MH(OPh)L2] (6 M = Ni 7 M = Pt) (L = phosphine) were examined (Eqs. 6.29, 6.30 Scheme 6-16), and a high nucleophiUdty for the metal-bound phenoxide was suggested [9, 10]. Reaction with methyl iodide produced anisole and trans-[MH(I)L2] for both Ni and Pt complexes. Phenyl isocyanate also provided the insertion products into the metal-phenoxo... 

A3-Pyrroline formation with carbonyl insertion also occurs during the reaction of /V-sulfinylarylamines with diphenylcyclopropenone in the presence of nickel carbonyl (Scheme 36).64 Phenyl isocyanate does not give a pyrroline product under these reaction conditions, hence the SO-CO exchange probably occurs within an intermediate metallocycle. The reaction... 

Zirconium and hafnium dialkylamides are highly reactive compounds. They undergo (i) protolytic substitution reactions with reagents such as alcohols, cyclopentadiene and bisftrimethylsilyOamine 63 64 (ii) insertion reactions with C02, CS2, COS, nitriles, phenyl isocyanate, methyl isothiocyanate, carbodiimides and dimethyl acetylenedicarboxylate 69-72 and (iii) addition reactions with metal carbonyls.73 These reactions are summarized with reference to Zr(NMe2)4 in Scheme 1. 

When a toluene solution of a mixture of cyclotrisilane 34 and cyclohexyl isocyanate (or f-butyl isocyante) was heated at 70 °C, cyclic di- and trisiloxanes 37 and 38, i.e. the cyclic dimer and trimer of the silanone 36, were obtained together with the corresponding isonitrile RN=C. The formation of 37 as well as 38 was completely suppressed in the presence of hexamethylcyclotrisiloxane (19 D3) instead, quantitative conversion of 35 into 39, the formal insertion product of the silanone 36 into the Si—O bond of D3, occurred (Scheme 14). Since neither cyclodisiloxane 37 nor cyclotrisiloxane 38 reacted with D3 under the reaction conditions, the possibility that 37 or 38 is the precursor of 39 was ruled out. Whereas the oxidation of 35 with cyclohexyl and t-butyl isocyanates proceeded with exclusive formation of 37 and 38 (as the silicon-containing compounds) the reaction of 35 with phenyl isocyanate resulted in the formation of 37 in low yield. Furthermore, in this case the presence of D3 did not totally suppress the formation of 37. According to the authors, these results indicate that the oxidation of 35 with cyclohexyl and f-butyl isocyanates appears to use other reaction channels than that with phenyl isocyanate. 

A new series of niobium derivatives (62) of the IV-phenylurethanes has been obtained586 from the insertion reaction between niobium penta-alkoxides and phenyl isocyanate. Most of the products are yellow liquids, one is white and the rest are brown or black solids or semi-solids. They exhibit v(C=0) in the range 1690— 1730 cm-1. Insertion of up to three molecules of phenyl isocyanate occurs readily at... 

The reactions are exothermic at RT, but successive insertions into polyalkoxides may become more difficult e.g., three of the five ethoxy groups of tantalum pentaethoxide react exothermically at RT with phenyl isocyanate, but the remaining two react only after 5 h at 80°C . The importance of nucleophilic attack of the alkoxy oxygen on the isocyanate is illustrated by reaction of the mixed isopropoxy 2,2,2-trifluoroethoxy vanadium compound, where insertion occurs into the V-OPr-i bond d ... 

The metal-nitrogen bond in the adducts is often reactive toward protic reagents. The combination MOR/HOR can thus lead to overall formation of a carbamate by insertion of isocyanate into the M—O bond, followed by acidolysis of the adduct, as for the reactions of Bu3SnOMe/HOMe with phenyl isocyanate ... 

Two main pathways for the formation of the rearranged sulphamide 434 can be considered (equation 144). Path B involves an intramolecular path for the formation of the sulphamide 434. However, when the reaction was carried out in the presence of phenyl isocyanate, the urea (441) was isolated from the reaction mixture. This provided evidence for the existence of free 2,2,4,4-tetramethylpyrrolidine (440), which was considered to arise from the tert-octyl nitrene (438) by y-hydrogen insertion. Later work401, however, showed that when the rearranged sulphamide is heated in the presence of phenylisocyanate under identical conditions to those for its formation, pyrrolidinylurea (441) is formed in 60% yield. Thus the formation of 441 is not evidence of the existence of free 440, because 434 once formed is capable of dissociation and reaction with phenylisocyanate to give 441. In addition, attempts to independently generate tert-oc y nitrene failed to produce any... 

Takai and co-workers used C-H insertion to generate several 2,3-disubstituted furans. Reaction of 3-/-butyliminofuran with phenyl isocyanate in the presence of a rhenium catalyst gave the desired disubstituted furan in good yield. 

Alper carried out reaction of A-cyclohexyl-2-vinylazetidine with phenyl isocyanate at room temperature and obtained the 4-vinyltetrahydropyrimidin-2-one in high yield. Formal insertion of C=N bond of isocyanate occurred as explained by 247b [90]. 

I have also included in this book the insertion reactions of carbon cumulenes into polarized metal single bonds, which can be perceived as an initial [2+2] cycloaddition, which subsequently rearranges to give a linear adduct. The reactivity of the metal substituent appears to be NR2 > OR > SR. When the metal compound contains several reactive groups, stepwise insertion occurs. For example, Sn(OR)4 reacts with phenyl isocyanate to give the tetracarbamate Sn[N(Ph)COOR]4. Mixed insertion products are obtained using different isocyanates. In the insertion reactions of carbodiimides sometimes ionic cyclic amidinate complexes are formed. 

Hydrogen cyanide adds to aliphatic and even better to aromatic isocyanates, in the presence of triethylamine, to give the expected insertion product 240. Instead of the highly toxic hydrogen cyanide, aqueous potassium cyanide can be used in the reaction with phenyl isocyanate... 

Insertion reactions of isocyanates into the C-NR2 bond of R2NCH2NHCOOR and R2NCH20R and into the C-OR bond in R2NCH(OR)2 are also known. In the reaction of (RS)2CHNR2 with isocyanates, an insertion into the C-SR bond occurs The cyclic trimer obtained from formaldehyde and aniline 254 reacts with phenyl isocyanate at 130 °C to give the 1,3,5-triphenylhexahydro-5-triazine-2-one 255. The reaction most likely proceeds by dissociation of the trimer to a 1,4-dipolar intermediate which adds phenyl isocyanate. 

Bis(dimethylamino)phenylborane reacts with phenyl isocyanate to give a 1 1 insertion product . Using excess isocyanate and heat, the 2 1 insertion product is obtained. Likewise, reaction of 268 with sulfonyl diisocyanate gives the heterocycle 269 . ... 

Triethylindium gives a mono insertion product 275 in the reaction with phenyl isocyanate... 

Also, Group IV elements, other than the carbon derivatives already discussed, undergo insertion reactions with isocyanates. Both Sn(n) and Sn(iv) compounds react readily with isocyanates and insertion into Sn-C, Sn-0 and Sn-N bonds are observed. Tin(n) dimethox-ide reacts with phenyl isocyanate to give the double insertion product 276. ... 

The reaction of Sn-N bonds with isocyanates also gives rise to the formation of insertion products. For example, trimethyltin dimethylamine reacts with phenyl isocyanate to give the expected insertion product 282 . 

Cyclosilazane (R2SiNR) reacts with phenyl isocyanate at 60-90 °C to give the six-membered ring insertion products in high yield Silylated imines 289 react with one equivalent of isocyanate to give the insertion products 290, which on further reaction with a different isocyanate afford 5,6-dihydro-l,3,5-triazine-2,4(l//,3i/)-diones 291 with two different substituents . 

Insertion into a Pb-OR bond is observed in the reaction of triphenyl or tributyl lead methoxide with a-naphthyl isocyanate however, trimeyhyl lead methoxide causes trimerization of the isocyanates. Careful addition of cyclohexyl- or phenyl isocyanate to tributyllead-A -diethylamine affords the insertion product 305. Reverse addition leads to trimerization. 

Reaction of n-butyl- or phenyl isocyanate with P(OSiMe3)3 affords the insertion products 321 5 ... 

Dimolybdenum and ditungsten hexaalkoxides (M = Mo, W) react with phenyl isocyanate to give the double insertion products 327. In this reaction, migration of two alkoxy groups also occurs. 

When the reaction flask containing the toluene solution of polyol has reached 40 °C, pipette into this flask 50 cm of normal phenyl isocyanate stock solution (at 25 °C), allowing a 15 s pipette draining time. No reaction occurs between polyol and phenyl isocyanate in the absence of Dabco catalyst. Leave the mixture for 15 minutes to reach thermal equilibrium. Transfer, by pipette, 50 cm of stock 0.56% wiv Dabco solution from the storage vessel (thermostatted at 25 °C) into a dry 50 cm volumetric flask. Remove the B34/B24 sampling adaptor from the reaction flask assembly and insert the neck of the 50 cm volumetric flask into the B34 socket to introduce the Dabco catalyst into the reaction mixture. Allow a 15 s draining time for the Dabco flask and replace the B34/B24 sampling adaptor. Start the stopwatch at the same moment that the Dabco solution is first tipped into the reaction flask, (i.e., at the exact moment that the Dabco catalysed reaction between polyol and phenyl isocyanate commences). 

H)-Oxazolones are formed by the spontaneous cyclization of /3-oxo isocyanates (equation 134). Similarly, o-hydroxyphenyl isocyanate, produced by the Curtius rearrangement of the azide of salicylic acid or by the action of sodium hypochlorite on salicylamide, forms benzoxazolone (equation 135). An analogous reaction is the formation of IV-phenyl-benzoxazolone by the action of thionyl chloride on the hydroxamic acid shown in equation (136) (78TL2325). Pyrolysis of aryl azidoformates affords benzoxazolones by nitrene insertion (equation 137) (81CC241). 

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