Carbamate bridged

The main chains in 46 are held together by a hydrogen-bonding assembly of capsules, and multiple carbamate —N" H3 O C(0)NH— bridges cross-link these chains. This is a 3D network, since the side amine groups are oriented in aU three directions. The carbamate bridges were detected by NMR spectroscopy. 

Anti-anti bridging of the carbamate ligand is thought to occur in the tin(IV) complex MejSn(02CNR2), while the tetrameric uranium complex U402(02CNR2)i2 provides an authentic example of a monatomic (tridentate) carbamate bridge between two metal atoms. 

Carbamate bridges were supposed to be superior to the isosteric carbonate analogs by having greater pH stability. The first S -O-S -N-caibamate-bridged dimer of thymidine was synthesized in 1974 by Gait et al., who obtained it in 38% yield by condensation of 3 -0-(2,2,2-trichloro-ethyl)carbonate of 5 -0-tritylthymidine with 5 -amino-5 -desoxy-thymidine (24) (Fig. 14). 

Gait et al. reported the first synthesis of a 3 5 carbamate-bridged dimer of... 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

Cp derivatives (Scheme 185) to form -oxo-bridged dimeric complexes. The stabilities of the Af,0-bound carbamate intermediates depend mainly on the cyclopentadienyl ring substituents, but there is also a small dependence on the nature of the length of the (dimethylamino)alkyl chain for the C5H4Me systems. ... 

Crystal structures of dinickel complexes with 0,0-bridging and 0,N-bridging (O-methylated) carbamate have been reported.2074,20 (874) produces one equivalent of ammonia upon heating in methanol/water solution.2082... 

A chiral diphosphine ligand was bound to silica via carbamate links and was used for enantioselective hydrogenation.178 The activity of the neutral catalyst decreased when the loading was increased. It clearly indicates the formation of catalytically inactive chlorine-bridged dimers. At the same time, the cationic diphosphine-Rh catalysts had no tendency to interact with each other (site isolation).179 New cross-linked chiral transition-metal-complexing polymers were used for the chemo- and enantioselective epoxidation of olefins.180... 

Cholesterol as well as unsaturated or saturated hydrocarbon chains are used as lipophilic lipid anchors. Although Cl 8-hydrocarbon chains (oleoyl or oleyl unit) are only used in unsaturated compounds, structural variations with C14-, C16-, or even Cl 8-hydrocarbon chains in saturated compounds are known (27). The lipophilic units are linked with a parent structure (usually glycerol) via ether (e.g., DOTMA) or ester bridges (e.g., DOTAP). Ester bridges are often used to create the linkage to avoid cytotoxicity, because ether bonds are more difficult to break down biologically than ester bonds (58). Substances that are easy to decompose and are therefore often used as a spacer are carbamate units (29) [e.g., 3p-[A-(A, A -dimethylaminoethyl)carbamoyl]-cholesterol (DC-Chol)], amide units, or phosphate esters. However, a direct correlation between toxicity and the... 

For cis-1 adducts, open valence isomers are favored for imino addends with planar imino bridges such as carbamates and the closed isomers are favored for imino addends with pyramidalized imino bridges such as alkylimines or NH. 

The observation that polyatomic, oxygen-rich groups can bridge between two Group 13 metal centres has already been discussed in the context of aluminium carbamates and carboxylates. However, a similar coordinative... 

Whereas the Hofmann rearrangement of the amidoalcohols 452 with the usual NaOCl did not occur, reaction of the oxygen-bridged 452 (X = 0) with bis(acetoxy)iodobenzene under mild conditions led to a 9 1 mixture of the corresponding cyclic and acyclic carbamate derivatives 197 and 453 (X = 0) (Equation 50). In the similar reaction of the methylene-bridged analog 452 (X = CH2), the product of perhydro-3,l-benzoxazin-2-one type 197 (X = CH2) was obtained exclusively <20030PP429>. 

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