Aryl-dialkyl

There are also examples in which phosphate esters of saturated alcohols are reductively deoxygenated.229 Mechanistic studies of the cleavage of aryl dialkyl phosphates have indicated that the crucial C-O bond cleavage occurs after transfer of two electrons.230... 

Aren- bzw. Alkanphosphonsaure-diphenylester lassen sich nach dieser Methode in guten Ausbeuten zu Aryl-dialkyl-228 bzw. Trialkylphosphanoxiden22y umsetzen. Tris-[diethoxyphosphoryl-methyl]-phosphanoxid liefert mit Phenyl-magnesiumbromid in Te-trahydrofuran Tris-[diphenylphosphinyl-methyl]-phosphanoxid zu 24% (Schmp, 230-235°)230. 

Metallic stannides can react with aryl halides,9 11 or phenols via the aryl dialkyl phosphates,12 13 or aryl ammonium salts,14 in a photostimulated SrnI reaction, for example ... 

The same change, from classical general base to nucleophilic catalysis by selected nucleophilic bases, has been observed and studied recently for the hydrolysis of activated amides (an example is l-benzoyl-3-phenyl-l,2,4-triazole 2.2, Scheme 2.11) [21], and is observed also for esters of various oxyacids of phosphorus. The changeover to general base catalysis of the hydrolysis of aryl dialkyl phosphates... 

The polymer was synthesized by polycondensation of an aryl dialkyl tri-azene compound containing a meta-COOH group in the aryl part and an OH-group in the alkyl part of the compound. Both the ablation characteristics (e.g., quality of ablation structure) and the properties of the polymer (e.g., low molecular weight (Mw), glass transition temperature (Tg) below room temperature, and the long synthesis time (>48 h)) were not satisfactory [120]. Therefore, we modified our approach to a two-step synthesis, shown in Scheme 2 [121, 122], which results in polymers of the general structure B in Scheme 1. 

For a more detailed analysis of the absorption properties, the UV spectrum of the model compound (Scheme 7), which was also synthesized, was calculated using semiempirical methods (MOPAC/ZINDO). The experimental UV spectrum of the model compound is nearly identical to the spectrum of the polymer. From the calculation it was derived that four UV transitions contributed to the absorption maximum at 330 nm. In detail, these are the HOMO LUMO, the HOMO->LUMO+l, the HOMO LUMO+2, and the HOMO—LUMO+3 transitions. The first two orbital excitations showed a large involvement of the triazene group, whereas the other two are mainly localized at the phenyl moieties. Similar results were previously reported for aryl dialkyl triazenes [119, 184] which have the same structural unit. Starting from simple chemical considerations, it could be thought that the number of chromophores responsible for the absorbance at around 300 nm is a low value, for example 2 or 4 per unit. On the other hand, the semiempirical calculations indicated the involvement of the phenyl moieties in the absorption properties therefore, the chromophore number in the calculation was not restricted to low values. As a starting point for the calculation, numbers close to the expected value were chosen. 

A simple consideration of typical values for N-N bond energies shows that they are in the range 1.5 to 3.0 eV (taken from hydrazine derivatives) [184], Therefore, both the 248-nm (5 eV) and the 308-nm (4 eV) excimer lasers are capable of breaking this bond directly. For aryl dialkyl triazene compounds, which exhibit a similar structural unit, a radical pathway of decomposition was reported [119, 140, 153]. The first step in this pathway is the homolytic bond cleavage between the N-N bond, creating a labile diazo... 

They have a lower biological activity and persistence than the aryl-dialkyl ureas discussed above, but their selectivity is greater. These derivatives can safely be used as selective weed killers in sensitive crops. 

Ammonia, mono and dialkyl or mono and diaryl amines form 1 1 adducts with organoaluminum compounds A1R3 (R = hydride, alkyl, aryl) at below 0°C and these split off hydrogen (from R2A1H) or alkane (from RjAl) on warming (12, 56, 73, 151, 152, 153,164, 330, 351) e.g., the products are dialkyl(aryl)-dialkyl(aryl)amino alanes ... 

A wide range of acyclic trisubstituted enones readily undergo ECA with both commercially available trialkylaluminium reagents and the in situ-generated aryl (dialkyl)aluminium reagents. Very low catalyst loadings are sufficient (0.5-3.0 mol %) and products are formed in good yields (33-95%) and exceptional enantio-selectivities (80 to 99%) (Scheme 28) [65]. 

Organotelluriumfll and IV) compounds undergo transmetallation with Pd(II)[414], The carbonylation of the alkenylphenyltellurium(II) 459 gives the a,/3-Unsaturated ester 460 and benzoate, 460 being the main product[415], Reductive coupling of diaryl, dialkyl, and aryl alkyltellurides 461 to give 462 proceeds by treatment with Pd(OAc)2[416,417],... 

The infrared spectra of a set of 2-thiazolylthioureas are reported in Ref. 486. The ultraviolet spectra of l-aryl-3-(2-thiazolyl)thioureas are characterized by two bands of approximate equal intensity around 282 and 332 nm (492). For l-alkyl-3-(2-thiazolyl)thioureas these bands are shifted to 255 and 291 nm, respectively (492). The shape of the spectrum is modified further when l.l -dialkyl-3-(2-thiazolyl)thioureas are considered (491). Fragmentation patterns of various 2-thiazolylthioureas have been investigated (100, 493), some of which are shown in Scheme 158. Paper and thin-layer chromatography provide an effective tool for the analysis of these heterocyclic thioureas (494. 495). 

The radical phenylation of a large number of mono- and dialkyl-thiazoles has been investigated (393,395,396,399-405, for a general review cf. 398) and analyzed in terms of partial rate factors. As in other instances the alkyl groups slightly activate the substrate in certain positions toward phenyl radicals, but they also induce some steric hindrance to the approach of the aryl radical from the onho positions (Fig. 1-19). 

This method has been applied to the synthesis of 4-methyl (659), 4-aryl (416, 519, 659), 4,5-dimethyl (137, 220, 221), 4,5-dialkyl (229, 681), 4-methyl-5-O-acetoxyethyl) (229), 4-methyl-5-(j3-carbethoxyethyl) (229), 4-ary 1-5-bromo (579), and 2-chlorothiazoles from the corresponding a-thiocyanatoketones (Table 11-28). 

In cationic polymerization the active species is the ion which is formed by the addition of a proton from the initiator system to a monomer. For vinyl monomers the type of substituents which promote this type of polymerization are those which are electron supplying, like alkyl, 1,1-dialkyl, aryl, and alkoxy. Isobutylene and a-methyl styrene are examples of monomers which have been polymerized via cationic intermediates. 

Inefficiencies ia the reaction with POCl leads to alternative production of trialkyl phosphates by employing the sodium alkoxide rather than the alkyl alcohol itself Dialkyl aryl phosphates are produced ia two steps. The low molecular weight alcohol iavolved (eg, butyl) first reacts with excess POCl. The neutral phosphate ester is then completed by the iatermediate chloridate reacting with excess sodium arylate ia water. 

Acyl peroxides of structure (20) are known as diacyl peroxides. In this structure and are the same or different and can be alkyl, aryl, heterocychc, imino, amino, or fiuoro. Acyl peroxides of stmctures (21), (22), (23), and (24) are known as dialkyl peroxydicarbonates, 00-acyl O-alkyl monoperoxycarbonates, acyl organosulfonyl peroxides, and di(organosulfonyl) peroxides, respectively. and R2 ia these stmctures are the same or different and generally are alkyl and aryl (4—6,44,166,187,188). Many diacyl peroxides (20) and dialkyl peroxydicarbonates (21) ate produced commercially and used ia large volumes. 

The 3 -heterocychcs ia the mid-distiUate range are primarily the thiacyclanes, ben2othiophenes, and diben2othiophenes. There are lesser amounts of dialkyl—, diaryl—, and aryl—alkyl sulfides (29). Alkylthiophenes are scarce or absent, but some evidence exists for ben2thiacyclanes (Fig. 6). As for the naphtha fractions, these sulfur species account for a minimal fraction of the total sulfur ia the cmde. 

Trialkyl esters of phosphonic acid exist ia two structurally isomeric forms. The trialkylphosphites, P(OR)2, are isomers of the more stable phosphonates, 0=PR(0R)2, and the former may be rearranged to resemble the latter with catalytic quantities of alkylating agent. The dialkyl alkylphosphonates are used as flame retardants, plasticizers, and iatermediates. The MichaeUs-Arbusov reaction may be used for a variety of compound types, including mono- and diphosphites having aryl as weU as alkyl substituents (22). Triaryl phosphites do not readily undergo the MichaeUs-Arbusov reaction, although there are a few special cases. 

Mono- and dialkyl derivatives can also be prepared using alkyl sulfates. Aryl chlorides are usually inert, unless activated by an electron-withdrawing group. Conversion to alkoxides allows formation of ethers. 

Hydrolysis of dialkyl sulfites under acidic and alkaline conditions, which is followed by the use of OH2, proceeds by attack at sulfur to give S—O cleavage (72). The rate of hydrolysis is generally faster for cycHc and aryl sulfites than for dialkyl sulfites (73). Activation parameters of hydrolysis are known for some sulfites, and the increased rate for ethylene sulfite results from a reduced entropy of activation which results from a rigid ring stmcture (74). 

N,N -dialkyl-/)-PDAs, N-alkyl-N -aryl-/)-PDAs, and N,N -diaryl-/)-PDAs. 

The N,]S -dialkyl-/)-PDAs are manufactured by reductively alkylating -PDA with ketones. Alternatively, these compounds can be prepared from the ketone and -lutroaruline with catalytic hydrogenation. The /V-alkyl-/V-aryl- -PDAs are made by reductively alkylating -nitro-, -nitroso-, or /)-aminodipheny1 amine with ketones. The AijAT-dialkyl- PDAs are made by condensing various anilines with hydroquinone in the presence of an acid catalyst (see Amines-aromatic,phenylenediamines). 

The first -PDA antiozonants were low molecular weight -diaLkyl-/)-PDAs which caused skin irritations. Current higher molecular weight -dialkyl or A/-alkyl-AT-aryl derivatives are not primary skin irritants. A notable exception is A/-(I-methylethyl)-A7-phenyl-/)-PDA, which causes dermatitis. However, since some individuals are more sensitive than others, antiozonants should always be handled with care (46). When skin contact does occur, the affected area should be washed with mild soap and water. In case of eye contact, flush weU with water. Inhalation of mbber chemicals should be avoided, and respiratory equipment should be used in dusty areas. 

Transesterification has become a convenient method for synthesi2ing high alkyl, aryl, or alkyl aryl carbonates. Fiber- and film-forming polycarbonates are produced by transesterifying dialkyl, dicycloalkyl, or diaryl carbonates with alkyl, cycloalkyl, or aryl dihydroxy compounds (62). 

A large number of pyridazines are synthetically available from [44-2] cycloaddition reactions. In one general method, azo or diazo compounds are used as dienophiles, and a second approach is based on the reaction between 1,2,4,5-tetrazines and various unsaturated compounds. The most useful azo dienophile is a dialkyl azodicarboxylate which reacts with appropriate dienes to give reduced pyridazines and cinnolines (Scheme 89). With highly substituted dienes the normal cycloaddition reaction is prevented, and, if the ethylenic group in styrenes is substituted with aryl groups, indoles are formed preferentially. The cycloadduct with 2,3-pentadienal acetal is a tetrahydropyridazine derivative which has been used for the preparation of 2,5-diamino-2,5-dideoxyribose (80LA1307). 

Carbon-sulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol (201) (700S(50)104). If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. 

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