Carbamates derivatives, from

Carbamates derived from chloroformates are used to manufacture pharmaceuticals, including tranquili2ers (58), antihypotensives, and local anesthetics, pesticides, and insecticides (see Carbamic acid). 

The carbamates, derived from the reaction of 8-aminoquinoline with phenyl or ethyl chloroformate, upon reduction with NaBH4 gave the... 

Allylsilanes are available by treatment of allyl acetates and allyl carbonates with silyl cuprates17-18, with antarafacial stereochemistry being observed for displacement of tertiary allyl acetates19. This reaction provides a useful asymmetric synthesis of allylsilanes using esters and carbamates derived from optically active secondary alcohols antarafacial stereochemistry is observed for the esters, and suprafacial stereochemistry for the carbamates20,21. 

Z)-3-Alkoxyallylstannanes of high optical purity are available by stannylation of lithiated allyl carbamates derived from optically active allyl alcohols118. 

Compounds which are of interest in this context include 4-oxadiazolylpyrid-azines (35, R = cyclopropyl, Et) [117], 6-aryloxy-2-hydroxyalkyI-3(27/)-pyri-dazinones [118], 3-halo-6-hydrazinopyridazines of type (36, R = substituted amino) [119], Ar-2-isoxazolylmethyl-substituted 3-iminopyridazines (37) [ 120], carbamates derived from 3,6-bis(hydroxymethyl)-4-pyridazinones (38, R = alkyl, Ph) [121], and iminodihydropyridazine derivatives (39, R1 = acyl R2 = H,MeS R3 = aryl) [122, 123]. In Hungary, antidepressant activity has been observed with some 3,6-disubstituted pyridazines of type (40) [124]. 

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... 

Enantioselective protonation of ketone metal enolates constitutes an important method for the preparation of optically active ketones. Fuji and coworkers have shown interest in the magnesium countercation in the enantioselective protonation of such enolates. Pertinent results are obtained with protonation of Mg(II) enolates of 2-alkyltetralones and carbamates derived from l,l -binaphtalene-2,2 -diol as chiral proton sources, as indicated in equation 82 and Table 11. 

The /V./V-dimethyl carbamates derived from 5-, 7-, and 8-hydroxyquino-lines 366, 368, and 370 were regioslectively converted into products 367, 369, and 371, respectively, using the LDA/TMSC1 equilibrium shift procedure (Scheme 113) [87JOM(336)l]. 

Abstract—The nature of the product of the reaction between an aminated silane and carbon dioxide was re-examined with the aid of simple model compounds, several amines, and several aminosilanes. Since the reaction products previously proposed include the amine bicarbonate and a carbamate derived from the amine, ammonium bicarbonate and ammonium carbamate were studied as models for the anions. Carbon dioxide adducts of neat model amines were prepared and studied. Results from a variety of techniques are summarized. Among the most useful was Fourier transform infrared (FTIR) spectroscopy of fluorolube mulls. FTIR spectra were distinctive and assignments characteristic of the two species were extracted from the spectral data. Comparisons of these assignments with the products of the reaction between carbon dioxide and various amines were made. The results indicate that alkylammonium carbamates are the principal product. Nuclear magnetic resonance (NMR) spectra in D20 indicated much dissociation and were not helpful in defining the products. 

FIGURE 3 The chemical structures of cellulose benzoate, amylose benzoate, and carbamate derivatives. (From Ref. 32.)... 

Paleo, M. R. Lamas, C. Castedo, L. Dominguez, D. A new synthesis of phthalides by internal trapping in ortho-lithiated carbamates derived from benzylic alcohols. /. Org. Chem. 1992, 57, 2029-2033. 

Replacing the benzyl carbamate in 65 with a chiral carbamate derived from (R)-pantolactone generates diaster-eomeric molybdenum 1,2-dihydropyridine complexes 76 and 77, which are easily separable by crystallization <20000L3909>. Once separated, these chiral complexes 76 and 77 are easily converted to the more reactive methyl carbamate molybdenum 1,2-dihydropyridine complexes 78 and 79, respectively, and allow the synthesis of enantio-pure 2,6-disubstituted tetrahydropyridines (Scheme 21). 

Pirrung, M.C. and Huang, F C.-Y.D (1995) Photochemical deprotection of 3, 5 -dimethoxybenzoin (DMB) carbamates derived from secondary amines. Tetrahedron Letters, 36, 5883—5884. 

Further C6o derivatives of menthol include a menthyl malonate adduct119 and a carbamate derived from l,2-epimino[60]fullerene.429 Resin acid derivatives have been prepared by Diels-Alder reaction of C6o with methyl levopi-marate, whose parent acid can be isolated from rosin.430 Finally, a derivative of a-pinene was synthesized in the context of a study on the photochemically induced addition of allyl stannanes to Cr,o, a reaction presumably proceeding via SET from the stannane to the triplet excited fullerene.431... 

V-Sulfinyl carbamates derived from chiral alcohols show high enantioselectivity in Lewis acid catalyzed [2 + 2] and [4 + 2] cycloadditions with alkenes and 1,3-dienes, respectively. In the presence of 1.2 equivalents of tin(IV) chloride, the chiral /V-sulfinyl carbamate 5 derived from fraw-2-phenylcyclohexanol reacts with a variety of alkenes to give diastereomeric sulfmamide derivatives 691,98. Very high asymmetric induction at both sulfur and carbon is observed. A detailed discussion of this ene reaction and transformations of the ene adducts thus formed is given in Section D.4.6. 

The hydroxyamination of 2-phenyl-l-propene was carried out with the carbamates derived from ( )-9-(2,2,2-trihalo-l-hydroxyethyl)anthracene ( )-D and ( )-E and gave mixtures of regioisomers 3 and 4, each as a pair of diastereomers. It is surprising that the major regioisomer in these reactions is the primary alcohol 3. This is in contrast with the regioselectivity described for the catalyzed oxyamination reactions of 2-phenyl-l-propene with chloramine-T94, and 1-phenylcyclohexene with terf-butyl chloro(argento)carbamatc95. 

Less than 5% enantiomeric excess was obtained in the osmium-catalyzed oxyamination of 2-phenyl-l-propene when chiral carbamates derived from 1-menthol and 1-borneol were used96, but the structures of the resulting products were not reported. 

The use of the corresponding thiourea in this reaction leads to equal amounts of both diastereomers, that is, no stereoselectivity is observed48. Chiral carbamates, derived from (-)-menthol and (+ )-camphor, give, in a similar reaction, a-aminoalkanephosphonic acids with optical purity up to 42 %71. 

Alkyl carbamates, derived from 2,2,4,4-tetramethyl-1,3-oxazo-lidine (R-CH2-OCby), are deprotonated by s-Butyllithium- —)-sparteine with differentiation between the enantiotopic protons (eq 5). The pro-S proton is removed with high stereoselectivity and reliability, and, subsequently, stereospecifically substituted by electrophiles with stereoretention to give enantiomerically enriched secondary alcohols (>95% ee) after deprotection, ... 

The benzyloxycarbonyl (Cbz) group can be removed from nitrogen by BF3 Et20 in the presence of either a thiol or dimethyl sulfide. The carbamates derived from secondary amines are cleaved more rapidly than those from primary amines by use of the ethanethiol method, even when using BF3 Et20 as solvent. This procedure is reasonably selective, as shown in Eq. (25) [46]. 

In the course of our attempts dedicated to the search of new pesticides, we were interested in the design of proinsecticides, especially procarbamates which are less toxic to mammalians than the parent carbamates. N-Acyl-N-methyl or N-sulfenyl-N-methyl carbamates derived from Carbofuran or Aldicarbe are quite effective insecticides and are often equal to superior to their parent compound against insects. 

Carbamate Derived from an Amine and CO2, 707 Methyl and Ethyl, 708 9-Fluorenylmethyl, 711... 

Yamada T, Lukac PJ, George M, Weiss RG (2007) Reversible, room-temperature ionic liquids. Amidinium carbamates derived from amidines and aliphatic primary amines with carbon dioxide. Chem Mater 19 967-969... 

Lawless. L.J. Blackburn. A.G. Ayling, A.J. Perez-Payan, M.N. Davis, A.P. Steroidal guanidines as enantioselective receptors for N-acyl a-amino acids. Part 1. 3a-guanylated carbamates derived from cholic acid. J. Chem. Soc., Perkin Trans. 1 2001, (11), 1329-1341. 

The chemoselectivity of the reaction favors insertion in the most electron-rich C—H bond available to produce an oxazolidinone (Eqs. (5.6) and (5.7)) [33, 49, 50). When a bicyclic system is formed, the C—H amination reaction leans toward the formation of the cis-isomer. The scope of the reaction is large and many examples of carbamates derived from primary and tertiary alcohols are known. The use of carbamates derived from secondary alcohols is, however, more limited to substrates having conformational bias and/or very reactive C—H bonds (benzylic and allyl-ic) [51, 52]. Otherwise the formation of the corresponding ketone is observed, probably via a hydride shift process, similar to what is observed in C—H bond insertion with metal carbene [53, 54). 

Tamam and co-workers demonstrated that N-tosyl carbamates derived from allenic alcohols readily cychze under buffered conditions (Scheme 33).That way, 1,3-oxazo-lidin-2-ones and l,3-oxazin-2-ones with an a-acrylate side chain are accessible in high yield. It is noteworthy that only small amounts of PdCl2 are necessary in these cases and only the trani -isomers are detected. 

Enantiomerically pure lactonic pheromones 607-611, of the carpenter bee, blacktailed deer, Japanese beetle, rove beetle, and Oriental hornet, respectively, have been synthesized from racemic cyano alcohols of type 612. The key to the success of the overall approach is the facile separation of diastereomeric carbamates derived from cyano alcohols of type 612 by automated multigram LC. The chosen approach also facilitates the assignment of absolute configurations to the lactone enantiomers and their precursors. In the case of 607, direct determination of enantiomeric purity and absolute configuration is also possible using the chiral solvating agent 2,2,2-trifluoro-l-(9-anthryl)ethanol [439]. 

Yamada, T., Lukac, P.J., M. George, M., Weiss, R.G. (2007). Reversible, room-temp)erature ionic liquids. Amidinium carbamates derived from amidines and aliphatic primary amines with carbon dioxide. Chemistry of Material, 19,967-969, ISSN 0897-4756 Yamada, T., Lukac, P.J., Yu, T., Weiss, R.G. (2007). Reversible, room-temp)erature, chiral ionic liquids. Amidinium carbamates derived from amidines and amino-add esters with carbon dioxide. Chemistry of Material, 19,4761-4768, ISSN 0897-4756... 

N. Delia Ga, B. Gabriele, G. Ruffolo, L. Veltri, T. Zanetta, M. Costa, Effective guanidine-catalyzed synthesis of carbonate and carbamate derivatives from propargyl alcohols in supercritical carbon dioxide, Adv. Synth. Catal. 353 (2011) 133-146. 

Simple chiral allenes have been prepared by the reaction of propargylic carbamates with lithium dialkylcuprates. The diastereomeric carbamates, derived from racemic propargylic alcohols and (/ )-1-(l-naphthyl)ethyl isocyanate, are readily separated by h.p.l.c. they are then treated with lithium dialkycuprates at -78 °C, producing the allenes with enantiomeric excess up to 80% in yields of around 70% (Scheme 2). The method is claimed to be an improvement on earlier methods in that it is much simpler and gives better optical yields. 

A related 1,3-rearrangement, also studied by Jorgensen, is the decarboxylative rearrangement of O-carbamates derived from MBH adducts, an aminereaction that also takes place via a domino Sn2-Sn2 mechanism (Scheme 40.27). 

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