Carbamate compounds mixtures

Pseudo-allyl compounds are formed from reactions of [Re(CO)2(PPh3)2(OCHNC6H4-4-Me)] with excess of PhNCO or PhNCS. Whereas carbamate compounds are formed in the former case, a mixture of monothio- and dithiocarbamate compounds is obtained with the sulfur analogue. The formation of the latter complex proceeds via the intermediate formation of the first. The related compounds show similar structural features with distorted octahedral rhenium atoms and... 

In the literature, few examples exist for combinatorial synthesis in solution [68], with most being one- or two-step parallel synthesis of individual compounds or reagent-mixture synthesis of compound mixtures. Pools of dimeric compounds including esters, amides and carbamates have been successfully prepared without needing further purification. One example of a reaction which is particularly applicable to combinatorial synthesis in solution is a multicomponent reaction, such as the Ugi four-component reaction, as it can produce four points of diversity in a single step [69-71],... 

In this context, the enantiomeric pair containing the eutomer of cyclothiazide can be resolved by HPLC on cellulose-derived coated CSPs. Nevertheless, the poor solubility of this compound in solvents compatible with this type of support makes this separation difficult at preparative scale. This operation was achieved with a cellulose carbamate fixed on allylsilica gel using a mixture of toluene/acetone as a mobile phase [59]. 

From intermediate 28, the construction of aldehyde 8 only requires a few straightforward steps. Thus, alkylation of the newly introduced C-3 secondary hydroxyl with methyl iodide, followed by hydrogenolysis of the C-5 benzyl ether, furnishes primary alcohol ( )-29. With a free primary hydroxyl group, compound ( )-29 provides a convenient opportunity for optical resolution at this stage. Indeed, separation of the equimolar mixture of diastereo-meric urethanes (carbamates) resulting from the action of (S)-(-)-a-methylbenzylisocyanate on ( )-29, followed by lithium aluminum hydride reduction of the separated urethanes, provides both enantiomers of 29 in optically active form. Oxidation of the levorotatory alcohol (-)-29 with PCC furnishes enantiomerically pure aldehyde 8 (88 % yield). 

A number of other symmetric dichalogeno carbamates have been employed in, for example, the deposition of ZnS by a dip-dry method186 from a chloroform solution containing an equimolar mixture of [Zn(S2CNBu2)2] and the thiolate compound [EtZn(SPr )]. Pyrolysis was carried out at 300 °C under N2 and the polycrystalline (cubic phase) films were free from oxide contamination. 

In many applications nowadays it is essential to link a mass spectrometer to the gas chromatography in order to achieve positive identification and sensitivity of analysis. Some 12 types of compounds are listed in Table 1.11(a) which are based on the application of this technique, viz. polyaromatic hydrocarbons, polychlorobenphenyls, dioxins, chloro, carbamate and triazine types of herbicides and pesticides, Diazinon, Dicamba, Imidazoline and Cyperquat herbicides and herbicide pesticide mixtures. 

The instability of primary nitramines in acidic solution means that the nitration of the parent amine with nitric acid or its mixtures is not a feasible route to these compounds. The hydrolysis of secondary nitramides is probably the single most important route to primary nitramines. Accordingly, primary nitramines are often prepared by an indirect four step route (1) acylation of a primary amine to an amide, (2) A-nitration to a secondary nitramide, (3) hydrolysis or ammonolysis with aqueous base and (4) subsequent acidification to release the free nitramine (Equation 5.17). Substrates used in these reactions include sulfonamides, carbamates (urethanes), ureas and carboxylic acid amides like acetamides and formamides etc. The nitration of amides and related compounds has been discussed in Section 5.5. 

The UK Pesticide Safety Directorate (PSD) has decided to use the TEF approach for assessment of combined risk from exposure to mixtures of acetyl cholinesterase inhibitors (organophosphate (OP) compounds and carbamates) (PSD 1999). Despite clear differences in the action of carbamates and OP compounds, the index compounds selected for all acetyl cholinesterase inhibitors were either aldicarb (carbamate) or chlorpyrifos (OP). The POD for determining relative potency was predetermined as the dose level that produced 20% inhibition of red blood cell cholinesterase in a 90-day dietary study in rats. 

As a rule, the thermal rearrangements of functionally substituted bicyclopro-pylidenes of type 107 yield mixtures of compounds (Scheme 21) [103,107,108]. But the methoxycarbonyl-substituted carbamate 53 underwent a clean regio-selective isomerization to give 54 as a single product [55]. 

Compounds bearing the 21-sulfo substituent are easily hydrolyzed to their corresponding carbamates (1,2,22,26,27,32-35). Due to the great increase in potency associated with this conversion and the difficulty of preventing it entirely, it is difficult to accurately determine the potencies of the sulfamates, or mixtures that contain them. 

The preference for 8-metalation, seen with the 2-phenyl-, 4-pivalamido-, and 2-butyl-5-ethoxyquinolines, is continued, as shown by the absence of any 6-substituted products from the directed lithiation of 7-substituted derivatives. This type of preference is not seen with 6-substituted compounds, however, and a mixture of the 5,6,7-trisubstituted, and both possible disubstituted products, was obtained on treatment of the lithio derivative of the 6-carbamate with TMSC1 at -78°C [78JOM(336)l]. 

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