Reaction diazopyruvates

The reaction of cyclohexene with the diazopyruvate 25 gives unexpectedly ethyl 3-cyclohexenyl malonate (26), involving Wolff rearrangement. No cyclo-propanation takes place[28]. 1,3-Dipolar cycloaddition takes place by the reaction of acrylonitrile with diazoacetate to afford the oxazole derivative 27[29]. Bis(trimethylstannyl)diazomethane (28) undergoes Pd(0)-catalyzed rearrangement to give the A -stannylcarbodiimide 29 under mild conditions[30]. 

Jackson and Manske described the decomposition of diazoacetic ester with indoles to give, after hydrolysis, the 3-acetic acid and some 1,3-diacetic acid no product of 2-substitution was found (see also ref. 49). Diazoacetone and diazopyruvic ester similarly gave the 3-sub-stituted indoles.Badger et al. have also examined the reaction of iV -methylindole, as well as of indole, with diazoacetic ester. Again only the 3-substituted product resulted and no evidence was obtained for addition. 

Many of the early workers who studied the thermal decomposition reactions of diazocarbonyl compounds found that the addition of copper metal or copper salts allowed the reaction to be achieved at a lower temperature,<63AG(E)565, 64CB2628, 73JOU431> although no detailed study of this catalytic effect was undertaken. Alonso and Jano studied the copper-salt reaction of ethyl diazopyruvate 26 with acetonitrile and benzonitrile. The... 

Section B gives some examples of metal-catalyzed cyclopropanations. In Entries 7 and 8, Cu(I) salts are used as catalysts for intermolecular cyclopropanation by ethyl diazoacetate. The exo approach to norbornene is anticipated on steric grounds. In both cases, the Cu(I) salts were used at a rather high ratio to the reactants. Entry 9 illustrates use of Rh2(02CCH3)4 as the catalyst at a much lower ratio. Entry 10 involves ethyl diazopyruvate, with copper acetylacetonate as the catalyst. The stereoselectivity of this reaction was not determined. Entry 11 shows that Pd(02CCH3) is also an active catalyst for cyclopropanation by diazomethane. 

For example, reaction of ethyl diazopyruvate with cyclohexene in the presence of rhodium 126) or copper113 126 catalysts furnishes, besides the 7-exo-substituted norcarane 108, a small amount of 110, which may arise either from allylic insertion or from the 7-mfo-substituted norcarane 109 by a thermal 1,5-homo-hydrogen shift. 

Ethyl diazopyruvate, under copper catalysis, reacts with alkynes to give furane-2-carboxylates rather than cyclopropenes u3) (Scheme 30). What looks like a [3 + 2] cycloaddition product of a ketocarbenoid, may actually have arisen from a primarily formed cyclopropene by subsequent copper-catalyzed ring enlargement. Such a sequence has been established for the reaction of diazoacetic esters with acetylenes in the presence of certain copper catalysts, but metallic copper, in these cases, was not able to bring about the ring enlargement14). Conversely, no cyclopropene derivative was detected in the diazopyruvate reaction. 

The reaction, formally speaking a [3 + 2] cycloaddition between the aldehyde and a ketocarbene, resembles the dihydrofuran formation from 57 a or similar a-diazoketones and alkenes (see Sect. 2.3.1). For that reaction type, 2-diazo-l,3-dicarbonyl compounds and ethyl diazopyruvate 56 were found to be suited equally well. This similarity pertains also to the reactivity towards carbonyl functions 1,3-dioxole-4-carboxylates are also obtained by copper chelate catalyzed decomposition of 56 in the presence of aliphatic and aromatic aldehydes as well as enolizable ketones 276). No such products were reported for the catalyzed decomposition of ethyl diazoacetate in the presence of the same ketones 271,272). The reasons for the different reactivity of ethoxycarbonylcarbene and a-ketocarbenes (or the respective metal carbenes) have only been speculated upon so far 276). 

The structure of the carbenoid has considerable effect on the outcome of the reaction with vinyl ethers. Unlike the case with diazoacetate, reaction with diazopyruvate resulted in the formation of a dihydrofu-ran (17) rather than a cyclopropane (equation 8).26d The reaction is a formal [2 + 3] cycloaddition but it... 

The Cope rearrangement of c/j-di vinylcyclopropanes is thermally allowed and offers an attractive stereoselective approach to cycloheptadienes. Cyclopropanation reactions can be used to prepare divi-nylcyclopropanes, as shown in Scheme 23.120 Reaction of ethyl diazopyruvate with butadiene generated... 

Under similar conditions diazo acetoacetate does not afford cyclopropanes but dihydrofurans as 62 which can be aromatized (e.g. to 63)20). A different furan derivative 64 is obtained from ethyl diazopyruvate as outlined in Eq. 19 38). Possibly cyclopropanes are intermediates in these reactions, which rearrange to the five-membered heterocycles under the conditions employed. 

Certain diazoketones, for example diazopyruvate, alkyl 2-diazo-3-oxobutyrate or 3-diazo-2,4-pentanedione, react with vinyl ethers under metal catalysis to give dihydrofurans rather than cyclopropanes l Most work on this type of transformation has been that of Wenkert and Alonsoand their respective groups. A representative example is shown in equation 107. Finally, carbenoid dimerization is also a competitive reaction in metal catalysed intermolecular cyclopropanation. However, control of the chemoselectiv-ity to favour the cyclopropanation is possible. In general, the dimeric product can be avoided by using excess of alkene or by very slow addition of the diazo compound to a mixture of alkene and catalyst... 

Dihydrofuran derivatives 319 are formed as major products in Rh2(OAc)4-catalyzed reactions of a-diazoacetophenone with 2-methoxy-propene or a-methoxystyrene (84MI1). Copper chelate or rhodium(II) acetate-catalyzed 1,3-dipolar cycloaddition of metal carbenoids, generated from ethyl formyldiazoacetate (90JOC4975), ethyl diazopyruvate... 

Oxepin 404 was prepared by the reaction of ethyl diazopyruvate with 1,3-butadiene in 26% yield. The reaction involves a carbene addition to the double bond with formation of a mixture of cis- and trans-2-oxo-2-(2-... 

Within the framework of the above methodology, 2-methylenedioxole 554 is accessible by trapping a carbene with ketene 555 (77JOM155). Ethyl diazoacetate reacts with substituted cyclohexanones in the presence of Cu(acac)2 in a similar manner to produce spirodioxoles 556 (80JHC721), while the reaction of ethyl diazopyruvate with ketone 557 furnishes the 1 2 adduct 558 [88CI(L)631],... 

A solution of ethyl diazopyruvate (6 5.00 g, 35.0 mmol) in dry CHjCl (400 mL) was added dropwise, within 8 h, into stirred suspension of rhodium(II) acetate dimer (20 mg, 0.04 mmol) in dry CHjCl (100 mL), in which an excess of liquid buta-1,3-diene (i.e. gaseous butadiene liquefied in a dry ice/acetone condenser) had been dissolved. More butadiene was added periodically and the reaction (at rt) was monitored by TLC (silica gel, hexane/EtOAc 4 1) for the disappearance of the diazo ester. The mixture was concentrated to a 10-mL volume and column chromatographed (silica gel, hexane/EtOAc 12 1) to give colorless liquid 7 yield 2.06 g (35%). 

For example, reaction of ethyl diazopyruvate with cyclohexene in the presence of rhodium or copper catalysts furnishes, besides the 7-exo-substituted... 

Without the disadvantage of using diazo compounds in the first step, Wenkert s latest monoterpenoid syntheses would be most efficient approaches, and in any case represent novel routes to well-known materials. Nezukone (754) was the result of examining the reaction between butadiene and diazopyruvic ester catalyzed by rhodium tetraacetate. The major product of the addition was the cyclopropane 758 (Scheme 62). It was known that divinylcyclopropanes could be thermolyzed to cycloheptadienes (Vol.4, p.537, Ref.600). The Wittig product from 758 thus gives a cycloheptadiene, and subsequent steps are shown in the scheme. The last step involves Grignard addition to the ester function of the enolate, then loss of water and redistribution of the double bonds.(Further examples of the use of diazo compounds will be found under perillene in the section on furans.)... 

Reaction of 1,3-butadiene with diazopyruvate in the presence of dirhodium(ll) tetraacetate affords 35% of the acylcyclopropane 38, accompanied by dihydrooxepinecarboxylate 39 and dihydrofurancarboxylate 40 in 26% and 4% yield, respectively 865. Probably, cu-acylcyclo-propane (cis-38), which is not observed, immediately rearranges to 39, whereas trans-38 is stable under the reaction conditions. On the other hand, ci.v-2-vinylcyclopropanecarbaldehyde (41) is favored in the equilibrium with 2,5-dihydrooxepine (42) by 19 l49. This discrepancy in the reactivity of c /.v-38 and cis-41 has been explained by coulombic repulsion of the a-dicarbonyl system of rw-38. 

Reaction of 2,3-dihydro-1,4-dioxin with ethyl diazopyruvate over (trimethylphosphino)copper(I) chloride produces dihydrofuroic ester (114) and a similar reaction with dimethyl diazomalonate, followed by acid hydrolysis, afforded the lactone ester (115) <85JOC4681>. 

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