Isocyanates tert-butyl

Aryl Isocyanates Prepared with B0C2O ), afforded the alkyl isocyanates tert-butyl isocyanate 404 and 1,1,3,3-tetramelhylbutyl isocyanate 406 in yields of 49% and 97%, respectively [221], Isopropylamine can also be converted into the isocyanate by this method. As with tert-butyl isocyanate, isopropyl isocyanate has to be separated from the tert-butanol formed simultaneously. Consequently, its yield is reduced. In contrast, higher branched alkyl isocyanates, such as 406, can be isolated in quantitative yield. 

At this point the product consisted mostly of the isocyanate, since the reaction with tert-butyl alcohol is relatively slow at 35-40°. If the photolysis is carried out in an aprotic solvent such as tetrahydrofuran, the isocyanate may be isolated. However, care must be exercised to avoid losses of this rather volatile and moisture-sensitive compound. 

Treatment of N-tert-butylsulfonylamine 1321 with Li-HMDS 492 induces elimination of Me3SiOLi 98 and the formation of sulfurdiimide 1322 in 65% yield [92]. The analogous reaction of tert-butyl isocyanate 1323 with Li-HMDS 492 affords N-... 

Goodman and Chorev 75 found that the required a-aminoacyl azides 14 are best prepared by reaction of the mixed anhydride of the amino acid with sodium azide. This method led to slightly better yields than the nitrosylation of TV-formylaminoacyl hydrazide. Curtius rearrangement of the a-aminoacyl azide 14 yielded the isocyanate 16, which was subsequently trapped as 17 or 18 as shown in Scheme 2. Comparable yields were obtained by nitrosylation with tert-butyl nitrite. 76 Other methods of acyl azide formation have rarely been employed for PMRI-peptide synthesis. Only Fincham et al. 11 reported the use of trimethylsilyl azide to synthesize an acyl azide en route to a PMRI-peptide. 

Both alkyl and aryl isocyanates are found to trimerize upon heating or in the presence of catalysts to 1,3,5-trisubstituted hexahydro-x-tdazinetriones (18) (isocyanurates) (57). Only highly substituted isocyanates, such as tert-butyl isocyanate [7188-38-7] and tert-octyl isocyanate, fail to trimerize under these... 

Irradiation of a tert-butyl alcohol solution of 6-ethoxy-4,5-dihydro-2(3H> pyridone (14) under conditions similar to those described for 12 gives two products, tert-butyl N-(ethoxyethylidene)carbamate (27) in 15% yield and glutarimide in 23% yield18. There is no indication of formation of the cyclobutyl analogue of 13. In aprotic solvent, ethoxyvinyl isocyanate (28) and glutarimide (29) are the major photoproducts formed. The gaseous byproducts from the irradiation of 6-propoxy-... 

The interaction of the [Ph4P]+ salts of [Ru(0)2C13]-, [Ru(0)2C14]2 , and [0s(0)2Cl4]2- with excess tert-butyl isocyanate in acetonitrile forms the salts of the anions [MN Bu NC(0)NBu C12] (M = Ru or Os) (271). X-ray diffraction studies have shown the anions to have distorted square-pyramidal geometry with the nitrido groups in axial position [d(Os=N) = 1.629(7), d(Ru=N) = 1.588(6) A],... 

Fig. 6.38. Mechanism of the preparation of an isocyanate by acylation of anilines with tert-butyl dicarbonate in the presence of 4-(dimethylamino)pyri-dine. In the absence of this additive a tert-butyl carbamate would be produced instead of an isocyanate (cf. Figure 6.37.)...

Actoxy-2-(2-cyan-l-methyl-ethyl)-E19a, 804 (R-MgX-En) E2Ic, 2221 (Hydrazon OAc/R) 2-Acetoxy-2-(2-cyan-propyl)- EI9a, 804 (R- MgX + En) E21c, 2221 (Hydrazon - OAc/R) Bicyclo[4.1.0]heptan 7-tert.-Butyl-oxycarbonyl-7-isocyan- E21a,... 

Light stable PUR 111 was created by incorporation of 4-(2,3-dihydroxyprop-oxy)-2-hydroxybenzophenone during PUR synthesis [139]. Similarly, urethane based coatings may be stabilized by immobilization of approx. 5% of 4-hydroxy-5-tert-butyl-3-[2-(5-chlorobenzotriazolyl)]methyl-isocyanate, added into the reaction mixture during PUR synthesis [140]. 

Acesulfame potassium is synthesized from acetoacetic acid tert-butyl ester and fluorosulfonyl isocyanate. The resulting compound is transformed to fluorosulfonyl acetoacetic acid amide, which is then cyclized in the presence of potassium... 

This dimer reacts as two molecules of free 5- alkyli-soxazolyl-3-isocyanate with secondary amines or with alcohols to give the corresponding ureas or carbamates useful as agrochemicals or fine chemicals intermediates. For example, 3-amino-5-tert-butyl isoxazole is a key intermediate for 3- 5-tert-butylisoxazolyl)-1,1-dimethyl urea (common name Isouron) which is useful as a herbicide for sugar cane and other crops (Ref. 180) [Scheme 127]. 

Photolysis of 5-ethoxy-3,4-dihydro-2/f-pyrrol-2-one led to a ring contraction and formation of an isocyanate, and in t rr-butyl alcohol this was trapped as tert-butyl A-(l-ethoxycyclo-propyl)carbamate (15) in 70% yield. ... 

A more productive synthesis of 1-hydroxycyclopropylammonium chloride (19) entails the acid hydrolysis of 1-ethoxycyclopropyl isocyanate (20) or tert-butyl 1-ethoxycyclopropylcarbamate... 

Benzylaminoethylamine (123), 2-chloroacctaldchydc, tert-butyl isocyanate, and formic acid gave 4-benzyl-At-tert-butyl-l-formyl-2-piperazinecarboxamide (124) (MeOH—11, (). 23 C, 3 days 60%). 5 ... 

Newer examples of such reactions include the transformations 3 - 4. The isocyanates can be trapped with tert-butyl alcohol and isolated as the carbamates.19 20... 

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