Aryl isopropyl carbonates

Near-quantitative yields of aryl isopropyl carbonates were realized in a similar process when diisopropyl peroxydicarbonate was reacted with alkyl-substituted aromatics.794 Substitution is effected by a radical entity possessing a considerable ionic character. 

Cupric chloride Aryl isopropyl carbonates from arenes... 

Organophosphorus compounds. Phosphorus-carbon bond fonnation takes place by the reaction of various phosphorus compounds containing a P—H bond with halides or tritlates. Alkylaryl- or alkenylalkylphosphinates are prepared from alkylphosphinate[638]. The optically active isopropyl alkenyl-methylphosphinate 778 is prepared from isopropyl methylphosphinate with retention[639]. The monoaryl and symmetrical and asymmetric diarylphosphi-nates 780, 781, and 782 are prepared by the reaction of the unstable methyl phosphinate 779 with different amounts of aryl iodides. Tnmethyl orthoformate is added to stabilize the methyl phosphinate[640]. 

PMMA is not affected by most inorganic solutions, mineral oils, animal oils, low concentrations of alcohols paraffins, olefins, amines, alkyl monohahdes and ahphatic hydrocarbons and higher esters, ie, >10 carbon atoms. However, PMMA is attacked by lower esters, eg, ethyl acetate, isopropyl acetate aromatic hydrocarbons, eg, benzene, toluene, xylene phenols, eg, cresol, carboHc acid aryl hahdes, eg, chlorobenzene, bromobenzene ahphatic acids, eg, butyric acid, acetic acid alkyl polyhaHdes, eg, ethylene dichloride, methylene chloride high concentrations of alcohols, eg, methanol, ethanol 2-propanol and high concentrations of alkahes and oxidizing agents. 

O-Aryl-A X-dicyclohexylisoureas are synthesized by stirring mixtures of phenols with 2-3 mol equiv. of dicyclohexylcarbodiimide at 45-100 C for 1-3 d. Hydrogenations are accomplished in isopropyl alcohol or ethyl acetate at 20 °C and atmospheric pressure using 200-300 mg of 5% palladium on carbon or on calcium carbonate per 0.02 mol of the phenol. The hydrogenolysis can also be effected with the crude mixture of the O-arylisoureas and the unreacted carlx iimide using as much hydrogen as needed for hydrogenation of the excess carbodiimide. 

When the aryl ring was optimally substituted as in prochloraz (III), simple variations of the N-alkyl group (for example from propyl to isopropyl, butyl or pentyl), were permissible without much loss in activity as was substitution of either carbon atom of the ethyl portion of the aryloxyethyl group by a methyl group. In some cases the aryloxyethyl chain could be extended to aryloxypropyl without loss of activity, but this was not always true. 

We must also consider the relative reactivities of the bonds. In the absence of direct data, we can compare bond dissociation energies as a measure of relative reactivity. Table 11-3 shows some pertinent data collected from various sources [18, 19, 20, 21]. The carbon-sulfur dissociation energies for n-alkyl monosulfides and n-alkyl mercaptans lie within a narrow range. Whether the other sulfur linkage is to carbon, as in n-alkyl monosulfides, or to the hydrogen of a mercaptan has no major influence. There is a small but perceptible trend toward weaker bonding with secondary carbon (isopropyl) and with tertiary carbon (t-butyl) in the unsymmetrical methyl aryl monosulfides, a trend that is not firmly evident in the in the corresponding alkyl mercaptans. The vinyl-sulfur... 

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