Carbamate cyclic

The alkylurea 576 and oxamide 577 are formed by oxidative carbonylation of amines under CO pressure using Pd/C as a catalyst[518]. The urea formation proceeds under atmospheric pressure using PdCh and CuCl2[519]. The mono-and double carbonylations of / -aminoethanol (578 and 579) afford the cyclic carbamate (oxazolidinones) 580 and oxamide (morpholinediones) 581 [520,521]. 

The cyclic carbamate (oxazoIidin-2-one) 313 is formed by the reaction of phenyl isocyanate (312) with vinyloxirane[I92]. Nitrogen serves as a nucleophile and attacks the carbon vicinal to the oxygen exclusively. The thermodynamically less stable Z-isomer 315 was obtained as a major product (10 I) by the reaction of 2-methoxy-l-naphthyI isocyanate (314) with a vinyloxir-... 

Miscellaneous lactams, cyclic carbamates, carbonates, ureas, etc.254... 

A cyclic carbamate (see also Chapter 7) is obtained in the reaction of an aminoalcohol with CDI [190]... 

Another fruitful investigation was based upon the cyanohydrin of ketone 60. This substance (75) undergoes hydride reduction to the corresponding aminoalcohol, which forms cyclic carbamate 76 on... 

The cyclic carbamate 329 under Pd-catalyst treatment in refluxing acetonitrile led to the formation of the corresponding bicyclic product 331. A plausible mechanism involves complexation of the Pd(n) catalyst to the triple bond, possibly helped by coordination to the aniline nitrogen, giving rise to the 7t-complex 330 (Scheme 47) <20030L1717>. 

Further variations for the synthesis of this ring system has been published by M. F. G. Stevens et al. (Scheme 12). Thus, the methyl-substituted cyclic carbamate 37 when treated with sodium nitrite in aqueous tartaric acid yielded temozolomide 9a in average yield (45%) <1997JOC7288>. Two other approaches also proved to be applicable to the synthesis of a great number of derivatives the diazoimidazole carboxamide 32 was reacted with various isocyanates to... 

Conversion to carbamates. Cyclic carbamates derived from sugars and related compounds have repeatedly been encountered, the first being an inosamine derivative, obtained by Curtius degradation of dihydroshikimic acid.82,83... 

Suzuki et al. [14] reported the Pd-catalyzed ring-opening polymerization of a cyclic carbamate in the presence of an initiator, which also acts as a core molecule, to afford a hyperbranched polyamine. The polymerization was proposed to be an in situ multibranching process, wherein the number of propagating chain ends increase with the progress of the polymerization. 

O-Ethyl cyclic carbamates (483) were reacted with Meldrum s acid (421) in boiling chloroform for 24 hr to give isopropylidene (1 -oxo-3-azacycloalk-2-ylidene)malonates (484) in 23-39% yields (86JHC701). 

Oxidative carbonylation is not necessarily associated with C - C bond formation. Indeed, heteroatom carbonylation may occur exclusively, as in the oxidative carbonylation of alcohols or phenols to carbonates, of alcohols and amines to carbamates, of aminoalcohols to cyclic carbamates, and of amines to ureas. All these reactions are of particular significance, in view of the possibility to prepare these very important classes of carbonyl compounds through a phosgene-free approach. These carbonylations are usually carried out in the presence of an appropriate oxidant under catalytic conditions (Eqs. 31-33), and in some cases can be promoted not only by transition metals but also by... 

H-1,3-Benzoxazine-2,4(3H)-dione (7.98) is an interesting cyclic carbamate. Hydrolysis of the ester group likely yields the ring-opened carbamic acid 7.99 as an undetected intermediate, which very rapidly decarboxylates to form the product salicylamide (7.100). When the cyclic carbamate was ad-... 

I. M. Kapetanovic, C. D. Torchin, C. D. Thompson, T. A. Miller, P. J. McNeilly, M. L. Macdonald, H. J. Kupferberg, J. L. Perhach, R. D. Sofia, J. M. Strong, Potentially Reactive Cyclic Carbamate Metabolite of the Antiepileptic Drug Felbamate Produced by Human Liver Tissue in vitro, Drug Metab. Dispos. 1998, 26, 1089 -1095. 

After selective cyclic carbamate formation, the 3 -OH can be selectively protected using THP (Scheme 4.14). The 5-OH was then glycosylated with a thiofuranose, creating a ribostamycin analog, 78. However, compound 78 was... 

When the ferf-butoxycarbonyl (Boc) carbamate-derived sulfone 5 was subjected to the Bi(OTf)34H20-catalyzed allylation conditions (Scheme 2), the cyclic carbamate 6 was obtained as the major product (36%, diastereoisomeric ratio (dr) = 82 18), along with the corresponding allylation product 7, although in low yield (16%). Such cyclic carbamate resulting from the internal capture of an intermediate (3-silyl cation with the Boc group and concomitant loss of isobutylene has already been reported in the literature [59]. 

Me and coworkers reported a novel oxidation reaction of Af-Boc-phenethyl amines 21a and 21b to the corresponding cyclic carbamate 22 and aldehydes 23a and 23b (equation 21). ... 

With the nitrogen atom well protected as the cyclic carbamate 105, all attempts to open the 1,6-anhydro ring under acidic conditions failed owing to the lability of the two allylic benzyl ethers present in the molecule. However, it was possible to debenzylate 105 with lithium in ammonia to form the new cyclic carbamate 108 and acetylation then gave 109. 

Cyclobutane-fused hexahydropyrimidine-2,4-dione 569 was converted to the corresponding l,3-oxazin-2-one derivative 571 in a two-step procedure (Scheme 109). Compound 569 was reduced with NaBH4 to give ureidoalco-hol 570 in excellent yield, the diazotization of which provided the cyclic carbamate derivative 571 <2006TL5981>. 

Silver fluoride/palladium(ll)-assisted cyclic carbamate formation from tm-butyldimethylsi-lyl (S )-( )-4-chloro-l-(2-methylpropyl)-2-butenylcarbamate to provide a 15 1 mixture of the 1,2-amino hydroxy system (for assignment, sec p 470)121. 

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