Diazo compounds, synthesis

Reaction of boranes with diazo compounds Synthesis of ketones from ethylene derivatives... 

Scandium Triflate-Catalyzed Rearrangement-Cycloaddition of 2,6-Diazasemibullvalenes and Diazo Compounds Synthesis of Triazabrexadienes... 

Cyclopropanes from diazo compounds Synthesis of polyenes... 

Reaction with Diazo Compounds Synthesis of 1-Imino-Pyrrole Derivatives... 

The problem of the synthesis of highly substituted olefins from ketones according to this principle was solved by D.H.R. Barton. The ketones are first connected to azines by hydrazine and secondly treated with hydrogen sulfide to yield 1,3,4-thiadiazolidines. In this heterocycle the substituents of the prospective olefin are too far from each other to produce problems. Mild oxidation of the hydrazine nitrogens produces d -l,3,4-thiadiazolines. The decisive step of carbon-carbon bond formation is achieved in a thermal reaction a nitrogen molecule is cleaved off and the biradical formed recombines immediately since its two reactive centers are hold together by the sulfur atom. The thiirane (episulfide) can be finally desulfurized by phosphines or phosphites, and the desired olefin is formed. With very large substituents the 1,3,4-thiadiazolidines do not form with hydrazine. In such cases, however, direct thiadiazoline formation from thiones and diazo compounds is often possible, or a thermal reaction between alkylideneazinophosphoranes and thiones may be successful (D.H.R. Barton, 1972, 1974, 1975). 

It was not their reactivity but their chemical inertness that was the true surprise when diazirines were discovered in 1960. Thus they are in marked contrast to the known linear diazo compounds which are characterized by the multiplicity of their reactions. For example, cycloadditions were never observed with the diazirines. Especially surprising is the inertness of diazirines towards electrophiles. Strong oxidants used in their synthesis like dichromate, bromine, chlorine or hypochlorite are without action on diazirines. Diazirine formation may even proceed by oxidative dealkylation of a diaziridine nitrogen in (186) without destruction of the diazirine ring (75ZOR2221). The diazirine ring is inert towards ozone simple diazirines are decomposed only by more than 80% sulfuric acid (B-67MI50800). 

There are several examples of intramolecular reactions of monocyclic /3-lactams with carbenes or carbenoids most of these involve formation of olivanic acid or clavulanic acid derivatives. Thus treatment of the diazo compound (106) with rhodium(II) acetate in benzene under reflux gives (107), an intermediate in the synthesis of thienamycin (80H(14)1305, 80TL2783). 

Synthesis of diazo compounds from active methyienas with tosyt azide (diazo transfer). 

The synthesis of thiepins 14 was unsuccessful in the case of R1 = i-Pr,79 but if the substituents in the ortho positions to sulfur arc /erf-butyl, then thiepin 14 (R1 = t-Bu R2 = Me) can be isolated in 99% yield.80 Rearrangement of diazo compound 13 (R1 = t-Bu R2 = H), which does not contain the methyl group in position 4, catalyzed by dimeric ( y3-allyl)chloropalladium gives, however, the corresponding e.w-methylene compound. The thiepin 14 (R1 = t-Bu, R2 = H) can be obtained in low yield (13 %) by treatment of the diazo compound with anhydrous hydrogen chloride in diethyl ether at — 20 C.13 In contrast, the ethyl thiepin-3,5-or -4,5-dicarboxylates can be prepared by the palladium catalysis method in satisfying yields.81... 

Of course, the key limitation of the ylide-mediated methods discussed so far is the use of stoichiometric amounts of the chiral reagent. Building on their success with catalytic asymmetric ylide-mediated epoxidation (see Section 1.2.1.2), Aggarwal and co-workers have reported an aza version that provides a highly efficient catalytic asymmetric synthesis of trans-aziridines from imines and diazo compounds or the corresponding tosylhydrazone salts (Scheme 1.43) [68-70]. 

In the 1980 s three monographs were published that cover parts of the present book, namely Quinone Diazides, by Ershov, Nikiforov, and de Jonge (1981), Aromatic Diazo Compounds, by Saunders and Allen (1985), and Williams Nitrosa-tion (1988). The book of Saunders and Allen which is actually the third edition of Saunders original book (1936, 1949), focuses on synthesis and preparative methods. The other two books emphasize rather the mechanistic and physical organic aspects of their subjects. 

Bis(diazo)-l,2,4,5-cyclohexanetetraone (4.5) may be regarded as a derivative of a double 1,2-quinone diazide. Its X-ray analysis was reported by Ansell (1969). The synthesis, properties, and structure of this interesting compound will be discussed in the forthcoming book on aliphatic diazo compounds (Zollinger, 1995, Secs. 2.3 and 5.2). 

Photo-de-diazoniation has found relatively little application in organic synthesis, as is clearly evident from the annual Specialist Periodical Reports on Photochemistry published by the Royal Society of Chemistry. Since the beginning of these reports (1970) they have contained a section on the elimination of nitrogen from diazo compounds, written since 1973 by Reid (1990). In the 1980s (including 1990), at least 90% of each report is concerned with dediazoniations of diazoalkanes and non-quinon-oid diazo ketones, the rest being mainly related to quinone diazides and only occasionally to arenediazonium salts. 

Spiroperidol, synthesis 230 (Z)/(ii)-Stereochemistry of aromatic diazo compounds 96 ff. 

Doyle MP, McKervey MA, Ye T (1998) Modern catalytic methods for organic synthesis with diazo compounds. Wiley, New York... 

Doyle, M.P. McKervey, M.A. Ye, T. Modem Catalytic Methods for Organic Synthesis with Diazo Compounds, Wiley, NY, 1998. 

More recently, Williams has described the one pot synthesis of 2-substituted oxazoles 11 by the thermolysis of triazole amides 9 the reaction does not proceed photo-chemically.<92TL1033> Although the reaction does not involve addition to a nitrile, it is an interesting application of a diazo compound since the proposed zwitterionic intermediate 10 is a resonance form of a diazo imine, so formally the reaction may be thought of as a thermal decomposition of a diazo imine (Scheme 6). 

Decomposition of diazo compounds by iron porphyrins is a convenient method for the synthesis of non-heteroatom carbene-iron porphyrins [22]. Reaction of [Fe(F2o-TPP)] [F20-TPP = meso-tetrakis(pentafluorophenyl)porphyrinato dianion] with diazo compounds N2C(Ph)R (R = Ph, C02Et, C02CH2CH=CH2) under an inert atmosphere afforded complexes [Fe(F2o-TPP)C(Ph)R] in 65-70% yields (Scheme 2). Like the halocarbene complex [Fe(TPP)(CCl2)], [Fe(F2o-TPP)CPh2] reacted with Melm to afford six-coordinate species [(MeIm)Fe(F2o-TPP)CPh2] in 65% isolated yield. 

Maas, G. Transition-metal Catalyzed Decomposition of Aliphatic Diazo Compounds — New Results and Applications in Organic Synthesis, 137, 75-253 (1986). 

DCA reactions are an important means of synthesis of a wide variety of heterocyclic molecules, some of which are useful intermediates in multistage syntheses. Pyrazolines, which are formed from alkenes and diazo compounds, for example, can be pyrolyzed or photolyzed to give cyclopropanes. 

These results can be interpreted in terms of competition between recombination of the diradical intermediate and conformational equilibration, which would destroy the stereochemical relationships present in the azo compound. The main synthetic application of azo compound decomposition is in the synthesis of cyclopropanes and other strained-ring systems. Some of the required azo compounds can be made by 1,3-dipolar cycloadditions of diazo compounds (see Section 6.2). 

Carbenes from Diazo Compounds. Decomposition of diazo compounds to form carbenes is a quite general reaction that is applicable to diazomethane and other diazoalkanes, diazoalkenes, and diazo compounds with aryl and acyl substituents. The main restrictions on this method are the limitations on synthesis and limited stability of the diazo compounds. The smaller diazoalkanes are toxic and potentially explosive, and they are usually prepared immediately before use. The most general synthetic routes involve base-catalyzed decomposition of V-nitroso derivatives of amides, ureas, or sulfonamides, as illustrated by several reactions used for the preparation of diazomethane. 

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