1- Diazo-2,5-dicarbonyl compounds

The rhodium-mediated reaction of 69 with 2,3-dihydrofuran (a formal dipolar cycloaddition of a cyclic diazo dicarbonyl compound with a vinyl ether) yields 70. Corrqiound 70 can be transformed in a number of steps to 71 a,b <96TL2391>. 

In conclusion, the rhodium-catalyzed reaction of diazo dicarbonyl compounds with nitriles provides direct access to useful classes of functionalized oxazgles. This direct, one-step pathway provides a significant improvement over past preparations. 

Readily available homopropargyl alcohols and diazo dicarbonyl compounds react in a novel formal [4 + 1]-cycloaddition to form various substituted tetrahydrofirrans with E-selectivity exclusively, involving a tandem O—H insertion/Conia-ene cychzation sequence through Rh(II)/Zn(II) cooperative catalysis (140L1004). 

Diazo acid chloride (26) can be prepared from compound (1). Chloride (26) Is an efficient reagent for preparing diazo dicarbonyl compounds from the corresponding alcohols or amines (eq 18). ... 

Copper-catalyzed reactions are particularly effective with a-diazo-P-dicarbonyl compounds such as diethyl diazomalonate. 

Diazo-1,3-dicarbonyl compounds such as alkyl 2-diazo-3-oxobutyrates 57a, b and 3-diazo-2,4-pentanedione 57 c behave like the diazopyruvate 56, as far as their carbenoid cycloaddition behavior is concerned 114,130). 

Diazomalonic esters, in their behavior towards enol ethers, fit neither into the general reactivity pattern of 2-diazo-l,3-dicarbonyl compounds nor into that of alkyl diazoacetates. With the enol ethers in Scheme 17, no dihydrofurans are obtained as was the case with 2-diazo-l,3-dicarbonyl compounds. Rather, copper-induced cyclo-propanation yielding 70 occurs with ethoxymethylene cyclohexane u4). However,... 

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 rhodium-catalyzed conversion of a-diazo-p-hydroxy carbonyl into P-dicarbonyl compounds (Table 23, Entries 6-8) in general seems to be preferable to the acid-catalyzed reaction because of higher yields and absence of side-reactions 37S,377). From a screening of 20 metal salts and complexes, Rh2(OAc)4, RhCl(PPh3)3, PdCl2 and CoCl2 emerged as the most efficient catalysts for the transformation of a-diazo-P-hydroxy esters into P-ketoesters 376). This reaction has become part of... 

As CH-acidic /3-dicarbonyl compounds, tetramic acids transform through a transfer of a diazo group with tosyl azide into a-diazoketones (80JHC1195) that may react further (74JA5787 89AP301). 

Enol Ethers and Esters 0-15 O-Alkylation of carbonyl compounds with diazo alkanes 0-17 Transetherification 0-20 Reaction between acyl halides and active hydrogen compounds 0-23 Transesterification 0-24 Acylation of vinylic halides 0-94 Alkylation with ortho esters 0-107 O-Acylation of 1,3-dicarbonyl compounds... 

Diazocarbonyl compounds can be prepared on insoluble supports by diazo group transfer with sulfonyl azides or by diazotization of primary amines. Diazo group transfer from sulfonyl azides to 1,3-dicarbonyl compounds proceeds on cross-linked polystyrene as smoothly as in solution (Table 10.19). When 3-keto esters or amides are... 

With a range of methods available for the formation of 1,3-dicarbonyl compounds, the dicarbonyl diazomethanes can be readily prepared via a simple diazo transfer reaction with sulfonyl azide. This has made a vast array of dicarbonyl diazomethanes available, which enhances the versatility in organic synthesis. A selection of examples from recent literature to illustrate the versatility of the cyclopropanation using dicarbonyl diazomethane in the construction of natural products as well as other biologically active compounds is described below. 

X-ray photoelectron spectroscopy, 139 Diazo ligands, 100 Dicarbonyl compounds reaction with amines aza macrocycles from, 902... 

Cyclization to a morpholinolactone (59) occurs in the hydrolysis reaction of the di-A-hydroxylethylated compound (60). Compound (59) is rapidly hydrolysed by water to (61) but in file presence of equimolar amounts of amines (RNH2) or ammo acid derivatives (62) forms.56 A novel reaction of cyclic 2-diazo-l,3-dicarbonyl compounds (63) with lactones (64) affords the products (65) in the presence of rhodium acetate, Rh2(OAc)4.57 Lewis acid-promoted intramolecular additions of allylsilanes to lilac tones gave substituted cyclopentanes.58 A proposed transition state guided efforts to improve the stereoselectivity of the reaction. The reaction of a series of /1-lactone derivatives, such as (66)-(68), has been studied and they have been ling cleaved the reaction outcome is both Lewis acid and structure dependent.59... 

Condensation of, J,iV-acetals 77 with 1,3-dicatbonyl compounds in the presence of mercury acetate leads to thiophenes 80. Mercury complexes 78 derived from 77 react with 1,3-dicarbonyl compounds to generate intermediates 79, which undergo cyclization and subsequent hydrolysis-deacylation to afford 80 <1998JOC6086, 2000JOC3690, 2000JHC363>. Thiophenes 82 <20020L873, 2004JOC4867> are also prepared by reaction of 77 with 2-diazo-3-trimethylsilyloxy-3-butenoate 81 (Scheme 18). 

The importance of a-diazo ketones as synthetic intermediates has led to the development of a number of general methods for their preparation.5 Particularly popular approaches include the acylation of diazo alkanes and the base-catalyzed "diazo group transfer" reaction of sulfonyl azides with 8-dicarbonyl compounds.6-7 While direct diazo transfer to ketone enolates is usually not a feasible process,8-9 diazo transfer to simple ketones can be achieved in two steps by employing an indirect deformylative diazo transfer strategy in which the ketone is first formylated under Claisen condensation conditions, and then treated with a sulfonyl azide reagent such as p-toluenesulfonyl azide.6a,6c,9,i0,11... 

Compared to diazonium salts, diazo compounds are generally much less reactive towards nucleophiles than towards electrophiles. As a result of this azo coupling reactions of diazo compounds are the exception rather than the rule. Electron withdrawing substituents on the diazo carbon increase the reactivity towards nucleophiles. Consequently the ability to undergo azo coupling reactions increases from diazomethane to diazocarbonyl- and 2-diazo-l, 3-dicarbonyl compounds. Among the earliest reactions known were those with cyanide and sulfite ions Tertiary phosphines, as opposed to amines, can form stable addition complexes with diazoalkanes probably due to the ability of phosphorus to stabilize the betaine with its empty d orbitals (6). 

Diazo-l,3-dicarbonyl compounds are electrophilic enough to give azo coupling products with reactive aromatic azo coupling components as well as with CH acidic compounds such as P-diketones and p-keto-esters. 

Excellent yields of diazo derivatives can be obtained by the reaction of the active methylene group in 1,3-dicarbonyl compounds. In this... 

The Rh2(pfb)4-catalyzed conversion of l-diazo-2,5-dicarbonyl compounds 364 occurs via cyclic carbonyl ylides 365 stabilized by 1,4-H-migration to produce dihydropyrans 366 in 60-85% yield (92JCS(P1)2837]. 

Regitz, M. Reaction of active methylene compounds with azides. I. New synthesis of a-diazo-P-dicarbonyl compounds from... 

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