Proefschrift--Leyden.

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Thesis (Ph. D.)--Catholic University of America, 1931. / Vita.

Thesis (Ph. D.)--Catholic University of America, 1930. / Biography. eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--Catholic University of America, 1931. / Vita.

The role of aryne intermediates in the reactions of acetylarylnitrosamines in solution has been investigated. Participation by 3-t-butylbenzyne in the decomposition of o-t-butyl-N-nitrosoacetanilide in benzene, leading to m-t-butylphenyl acetate, has been confirmed, although the major product, o-t-butylphenyl acetate, is formed predominantly from o-t-butylphenyl carbonium ions, 5-t-Butyl 1,4-dihydronaphthalene-1,4-endoxide has been isolated from the decomposition in the presence of furan. In common with the o-isomer, m- and p-t-butyl-N-nitroso-acetanilides yield 'aryne adducts' with 2,3,4,5-tetra- phenylcyclopentadienone in benzene. They do not, however, form t-butyl-l,4-dihydronaphthalene-l,4-endoxides with furan, and participation by a true aryne in their reactions and in those of unsubstituted N-nitrosoacetanilide, is discounted. The nature of the arynoid intermediato has not, in spite of the elimination of many possibilities, been conclusively established, but it is probably the dipolar conjugate base formed by removal of an o-proton from the arenediazonium cation. Anomalies similar to those observed in the decomposition of o-t-butyl-N-nitrosoacetanilide are exhibited by 2,5-di-t-butyl-N- nitrosoacetanilide, which affords aryne adducts with both furan and anthracene in greater yield than does the mono-substituted nitrosamide. Aryne participation was not evident in the highly complex decompositions in benzene of 1,4-di-t-butyl-2,5-di-(N-nitrosoacetamido) benzene, 2,5-di-t-butyl-2,5-di-(N-nitrosoacetamido)benzene, and 4-acetoxy-2,5-di-t-butyl-N-nitrosoacetanilide, Formation of 2,5-di-t-butylphenol, 2,5-di-t-butyl-2-benzoquinone, and acetic anhydride in the last-named reaction indicates deacetylation of the intermediate acetoxybenzenediazonium acetate, and suggests that complications in the reactions of the dinitrosamides arise from interaction between the N-nitrosoacetamido substituents. The decompositions of diphenyl[o-(N-nitrosoacetamido)phenyl] phosphine oxide and diethyl o-(N-nitrosoacetamido)phonyl]phosphonate have been studied, and evidence of aryne intermediacy obtained. The results are discussed in terms of currently acceptable mechanisms for the decomposition of N-nitroso- acetanilide and, where necessary, modifications to these are suggested.

As a synthetic procedure, the deoxygenation of aromatic nitro-compounds by tervalent organophosphorus compounds has been extended to include new routes to the anthranil and phenothiazine nuclei. Synthesis of anthranils from 2-nitrophenyl ketones has been exemplified by the preparation of 3-Phenylanthranil, 3-styrylanthranil and 5-chloro-3-methylanthranil from 2-nitro-benzophenone, 2 -nitrochalcone and 5-Chloro-2-nitroacetophenone respectively. The preparation of phenothiazines from 2-nitro-biaryl sulphides has been studied more extensively. It was found that when successful, this ring closure gave the cyclised product in about 55% yield. Rather more than half the sulphides used, however, gave no products or only a very low yield, and no rational means of predicting the success of a given ring closure could be found. Triethyl phosphite was the only phosphorus compound found to be capable of effecting this cyclisation. The use of several other phosphorus compounds was investigated, but although deoxygenation of the nitro-group undoubtedly took place, as evidenced by the large amounts of tar formed, no cyclised products could be isolated. Although a comprehensive investigation was not undertaken, the results of two experiments suggested that a considerable improvement in the yields of the phenothiazines could be achieved by carrying out the deoxygenations in a solvent (as opposed to pure phosphorus compound) and thus, reducing the extent of tar-forming side reactions. In addition, an unidentified product has been obtained from the reaction of 3-(o-nitrophenyl)coumarin with triethyl phosphate. Several unsuccessful attempts were made to synthesise a seven membered ring system. As part of an examination of the mechanism of the deoxygenation, the rate of reaction of a series of phosphorus compounds with 2-nitrobiphenyl was studied. It was found that phosphorus compounds with electron donating groups attached to the phosphorus atom reacted more rapidly, suggesting that the rate determining step involved a nucleophilic attack by phosphorus. No adequate explanation could be advanced for the finding that of all the phosphorus compounds studied, diethyl methylphosphonite reacted most rapidly. While the reactions of triethyl and triisopropyl phosphites were first order with respect to nitrobiphenyl, the reactions of hexaethyl phosphorous triamide and diethyl methylphosphonite appeared to be second order. A detailed kinetic study would be necessary to confirm this observation and investigate the fundamental change in mechanism which it implies. The possibility of the formation of nitroso-compounds as intermediates in the deoxygenation of the nitro-compounds has been discussed, and an unsuccessful attempt to trap such an intermediate has been made. Further attempts ought to be made in this direction and should be concentrated on finding a compound which will react more rapidly with the nitroso-compound than does triethyl phosphite. Such a trapping agent must also be capable of operating in the presence of an excess of nitro-compound. Much of the work in this thesis has been directed towards establishing whether an electron deficient nitrene intermediate is formed during the course of the deoxygenation of an aromatic nitro-compound. Although no one experiment could be regarded as conclusive, the overall weight of evidence argued convincingly in favour of this type of intermediate.

The reactions of tervalent phosphorus reagents with a number of aromatic nitro-compounds have been investigated. While it was expected that such reactions would give further examples of the deoxygenation and further reaction of the nitro-group, possibly via a reactive nitrene intermediates in fact, two, different, novel displacements of the nitro-group were found. In the first case, reaction of o-dinitrobenzene and related compounds with tervalent phosphorus reagents gave a series of phosphonates, phosphinates and phosphine oxides, in high yield, with the phosphorus atom bonded directly to the aromatic system, generally with an o-nitro-group still present in the final product. A mechanism involving nucleophilic aromatic substitution by the phosphorus reagent, with the displacement of the nitro-group as ethyl nitrite, was suggested. In the second case, reaction of p-nitrotoluene and p-ethylnitrobenzene, for example, with triethyl phosphite, gave low yields of diethyl p-tolyl- and p-ethylphenylphosphonate. As there is no activation of this nitro-group towards aromatic nucleophilic substitution, a mechanism involving attack on an oxygen of the nitro-group by the phosphorus reagent, with sub- sequent rearrangement through a four-membered intermediate was proposed. The other products of the reactions of o-alkyl-nitrosobenzenes and alkylnitrobenzenes with trialkyl phosphites were, in general, indicative of the participation, in the reaction, of a nitrene intermediate. The similarity of the products formed to those found in established examples of the reactions of nitrene intermediates, was noticed. The mechanism of this reaction was discussed in detail.