Wolff rearrangement chemistry

The workhorse of the VLSI industry today is a composite novolac-diazonaphthoquinone photoresist that evolved from similar materials developed for the manufacture of photoplates used in the printing industry in the early 1900 s (23). The novolac matrix resin is a condensation polymer of a substituted phenol and formaldehyde that is rendered insoluble in aqueous base through addition of 10-20 wt% of a diazonaphthoquinone photoactive dissolution inhibitor (PAC). Upon irradiation, the PAC undergoes a Wolff rearrangement followed by hydrolysis to afford a base-soluble indene carboxylic acid. This reaction renders the exposed regions of the composite films soluble in aqueous base, and allows image formation. A schematic representation of the chemistry of this solution inhibition resist is shown in Figure 6. 

Zeller, K.-P. Blocher, A. Haiss, P. Oxirene participation in the Photochemical Wolff Rearrangement Mlnl-Revlewx in Organic Chemistry 2004,1, 291-308. (Review). 

In contrast to the carbene and carbenoid chemistry of simple diazoacetic esters, that of a-silyl-a-diazoacetic esters has not yet been developed systematically [1]. Irradiation of ethyl diazo(trimethylsilyl)acetate in an alcohol affords products derived from 0-H insertion of the carbene intermediate, Wolff rearrangement, and carbene- silene rearrangement [2]. In contrast, photolysis of ethyl diazo(pentamethyldisilanyl)acetate in an inert solvent yields exclusively a ketene derived from a carbene->silene->ketene rearrangement [3], Photochemically generated ethoxycarbonyltrimethyl-silylcarbene cyclopropanates alkenes and undergoes insertion into aliphatic C-H bonds [4]. Copper-catalyzed and photochemically induced cyclopropenation of an alkyne with methyl diazo(trimethylsilyl)acetate has also been reported [5]. 

Background information on the chemistry of oxirenes is presented in Chapter 1.03, and this area has been reviewed by Zeller <2002SOS(9)19>. The potential antiaromatic character of oxirenes, the strain of the unsaturated three-membered ring, and the possible involvement in important reactions (e.g., oxidation of alkynes, Wolff rearrangement)... 

Knowledge that silyl substituents may be incorporated into standard resist chemistry to effect etching resistance has prompted several workers to evaluate silylated novolacs as matrix resins for conventional positive-photoresist formulations. Typically, these resists operate via a dissolution inhibition mechanism whereby the matrix material is rendered insoluble in aqueous base through addition of a diazonaphthoquinone. Irradiation of the composite induces a Wolff rearrangement to yield an indenecarboxylic acid (Figure 4), which allows dissolution of the exposed areas in an aqueous-base developer (35). 

The ester group in II is suggestive—although it is not a proof—of the intermediacy of a ketene, and ketene production in diazocarbonyl chemistry usually implies a Wolff rearrangement. The construction of a three-carbon chain on the other side of the ketone is a confirmation of this prediction. In turn, the Wolff rearrangement requires an a-keto carbene precursor that is the fate of diazo compounds exposed to ultraviolet light (wavelength lower than 3200 A). All this is translated into the mechanism depicted in Scheme 43.1. 

Bargon, J., Tanaka, K., Yoshimine, M. Computer chemistry studies of organic reactions the Wolff rearrangement. Comput. Methods Chem., [Proc. Int. Symp.] 1980, 239-274. 

Calvo-Losada, S., Sordo, T. L., Lopez-Herrera, F. J., Quirante, J. J. The influence of protecting the hydroxyl group of P-oxy-a-diazo carbonyl compounds in the competition between Wolff rearrangement and [1,2]-hydrogen shift. Density functional theory study and topological analysis of the charge density. Theoretical Chemistry Accounts 2000,103,423-430. 

Sato, T., NIIno, H., Yabe, A. Ketene Formation In Benzdiyne Chemistry Ring Cleavage versus Wolff Rearrangement. J. Am. Chem. Soc. 2003, 125, 11936-11941. 

In a sense the discoveries of Wolff and Schrbter were ahead of their time, for over 20 years were to pass before convenient methods for the preparation of the diazo ketones became available. Hence, synthetic applications largely date from the early 1930s. Periodically since then a number of substantial reviews of the Wolff rearrangement have been published, testifying to the importance that the reaction has achieved in preparative organic chemistry. Diazo ketone chemistry has achieved modem commercial importance in the photolithography industry. ... 

Reaction of 2-phenyloxazole-4-carbonyl chloride with diazomethane affords the crystalline diazomethyl ketone, which fails to undergo the Wolff rearrangement.389 In general the esters are smoothly hydrolyzed by aqueous alkali, but attempts to hydrolyze 5-aminooxazole-4-car-boxylates result in disruption of the ring system.389 The behavior of oxazole-4-carboxylic acids has been described in greater detail in The Chemistry of Penicillin .2... 

The photoinduced Wolff rearrangement of 5-diazo-2,2-dimethyl-l,3-dioxan-4,6-dione has also been examined by TRIR methods [116], These ultrafast measurements, conducted in a PMMA matrix, revealed that the formation of the ketene rearrangement product was complete within 20 ps a carbonyl carbene was not detected in this study. Other applications of TRIR spectroscopy to the study of carbene-related chemistry include investigations of diazirine to diazo rearrangements [117] and of oxygen and sulfur atom transfer reactions [118]. 

Davis, J.R., Kane, P.D., Moody, C.J. and Slawin, A.M.Z. (2005) Control of competing N-H insertion and Wolff rearrangement in dirhodium(II)-catalysed reactions of 3-indolyl diazo-ketoesters. Synthesis of a potential precursor to the marine 5-(3-indolyl)oxazole martefragin A. The Journal of Organic Chemistry, 70, 5840-5851. 

If the ketene was produced via a Wolff rearrangement at low temperature then the carboxylic acid c.ster. should certainly form as a result of the room temperature exposure. In view of this we conclude that the mechanism for the vacuum electron beam exposure docs not involve a Wolff rearrangement. Instead we propose that-a carbene formed by loss of Aj from the diazoketone plays a central role in the chemistry that ensues after electron beam exposure. The propo.sed mechanism for the electron beam induced chemistry discu.ssed thus far is summarized in the scheme below. 

It was back in 1902 when Ludwig Wolff (1875-1919), a professor of analytical chemistry at the University of Jena, discovered the thermal rearrangement of ethyl 2-diazo-3-oxobutyrate in water to produce ethane-1,1-dicarboxylic acid, a reaction that has since been named after him Although it is now over 100 years old, the Wolff rearrangement is still alive and well, with prominent applications in modern synthetic organic chemistry. The main applications of the... 

The [2+2] cycloaddition between ketenes and imines (Staudinger reaction ) is a reliable route to p-lactams, a class of compounds with a fundamental role as antibacterial agents in medicinal chemistry and also as versatile synthetic intermediates. Although the Wolff rearrangement is usually not the preferred route for the formation of the ketene intermediate in these reactions, a... 

Significantly, the newly discovered reactivity of a-oxo-ketenes as dienophiles and dipolarophiles in cycloaddition reactions complements their known chemistry as 1-oxadienes. This important extension of the Wolff rearrangement opens up new strategic possibilities in retrosynthetic planning and considerably expands the scope of possible synthetic applications. These pathways remain largely to be explored. 

Ludwig Wolff (1857-1919) was bom in Neustadt in the Palatinate and was educated at the University of Wtirzburg and Munich Polytechnic. In 1891, he became Professor of Analytical Chemistry at Jena, where he worked with Ludwig Knorr. His name is associated with the Wolff-Kishner reaction (1911) and the Wolff rearrangement (1912). 

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