With carbamates

Imidazole carboxylates of polyethylene glycols prepared with CDI react with amines to give polyethylene glycols (PEG) with carbamate end groups.12071 For example, PEG-... 

Collector TX26 is composed of dialkyl sulphosuccinamate and a mixture of phosphoric acid ester modified with carbamic acid derivative (OMC123) in a ratio of 50 25 25. 

Substrates with carbamate-protected [81, 82] and even free hydroxyl groups [69] reacted similarly in a deprotonation-reprotonation sequence, the latter even with retention of the -configuration of an alkene such as 46 (Scheme 1.19). The analogous (E)-alkene also delivers only E-product. 

Analogously, mixtures of A-alkoxycarbonyl- and iV-tosyl-9-azabicyclo 3.3.11- and [4.2.1]nonanes were obtained by reaction of 3 with carbamates or p-toluenesufonamide in the presence of mercury(II) nitrate followed by in situ demercuration with sodium borohydride (equation 168)171,172. 

Allylic substitution with free carbamate nucleophiles was not accomplished until advanced catalyst precursors were developed. However, products from substitution with carbamate nucleophiles were generated by a decarboxylative allylation. In this process, the imidodicarbonate was shown to undergo decarboxylation to form the carbamate nucleophile, and reaction of the resulting carbamate with the 7i-allyliridium intermediate formed branched allylic carbamate products (Scheme 17) [92, 95]. 

Scheme 25 Allylic substitution with carbamate nucleophiles...

The downward systemic movement of ONCOL (structure given earlier), a new insecticide derived from carbofuran, has been observed (19). A significant amount of radioactivity was observed in the roots of cotton and bean plants treated topically at the base of bifoliate or trifoliated leaves with [carbamate carbonylONCOL. Downward movement of the radiolabeled material may be explained by hydrolytic degradation of the ethoxycarbonyl moiety in ONCOL to the carboxylic acid derivative, the acid function serving as a downward moving carrier. 

A current limitation of the amination methodology is encountered with carbamate esters derived from 2° alcohols (that is, 22 and 24 in Scheme 17.14). With some notable exceptions, substrates in this class often give only small amounts ( 0-20%) of oxazolidinone, and instead afford the corresponding ketones in variable yields. A similar observation has been made by Doyle for C-H insertion reactions with 1-indanol diazo-... 

In order to find a suitable catalyst for intermolecular hydroaminations of 1,3-dienes, several metal sources were screened for the reaction of diene la (4 equiv) with carbamate 2a, and Bi(OTf)3 gave promising results [21, 22], The optimization studies using Bi(OTf)3 are summarized in Table 1 and show that 10 mol% of... 

Table 5 Intermolecular hydroamination of various 1,3-dienes with carbamate 2d...

The process is carried out using whole cells of Rhodosponidium tomloides cultured in a yeast-like form to replace the C3 acetoxy group with carbamate. Public domain sources of information do not indicate how many, and which enzymes are involved for instance whether the same enzyme is involved in the reactions at the C3 and C7 positions. 

Significantly, silylcuprates react with carbamates with syn stereoselectivity59, similar to their reactions with organocuprates62, whereas other nucleofugal groups, such as acetate or methanesulfonate, are displaced in an anti fashion23,27,57. Thus, both enantiomeric (or epimeric) allenes can be obtained from the same propynyl alcohol precursor. 

Hydroamination of Alkenes Kobayashi et at. found that several transition metal salts displayed high catalytic activity in aza-Michael reactions of enones with carbamates, while conventional Lewis acids (BF3-OEt2, A1C13, TiCl4...) were much less active. 

Depending on the functionality of the stopper (amine 52 or phenol 71), the reaction affords rotaxanes with urea bonding pattern 72-74 or with carbamate units 75. In each instance the temperature had to be raised to 40°C to ensure rotaxane formation and, interestingly, the free axle 76 was the only one to be isolated. This indicates that the low solubility of the reactants and the dumbbells can be the limiting factor in rotaxane synthesis when diisocyanates are incorporated. Molecular recognition is still effective, and again the decisive pattern for molecular aggregation seems to be the initial amide bond. Furthermore the macrocycle confers solubility on the thread. 

Carbamoyl phosphate synthetases. The first of the individual steps in the urea cycle is the formation of carbamoyl phosphate.163 Carbon dioxide and ammonia equilibrate spontaneously with carbamic acid ... 

An alternative method for the synthesis of proline-related phosphonates is attractive because peptides with a C-terminal Prop(OPh)2 22 can be obtained directly (Scheme 15) J43l The real intermediate reacting with triphenyl phosphite remains unknown but it is very likely that it is a cyclic A-acyliminium ion. Thus, the reaction could be similar to the amidoal-kylation of triphenyl phosphite with carbamates and aldehydes. 

Ph3PAuOTf has been shown to catalyse intra- and inter-molecular hydroamination of unactivated alkenes with sulfonamides in a Markovnikov fashion.115 The same complex catalyses hydroamination of 1,3-dienes with carbamates (e.g. PhCH2OCONH2) and sulfonamides at room temperature.116 An intramolecular version of the hydroamination with the Cbz group (benzyloxycarbonyl) has also been reported. The latter... 

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