Diazoalkanes addition

Bis(phosphoranimine) ligands, chromium complexes, 5, 359 Bis(pinacolato)diboranes activated alkene additions, 10, 731—732 for alkyl group functionalization, 10, 110 alkyne additions, 10, 728 allene additions, 10, 730 carbenoid additions, 10, 733 diazoalkane additions, 10, 733 imine additions, 10, 733 methylenecyclopropane additions, 10, 733 Bisporphyrins, in organometallic synthesis, 1, 71 Bis(pyrazol-l-yl)borane acetyl complexes, with iron, 6, 88 Bis(pyrazolyl)borates, in platinum(II) complexes, 8, 503 Bispyrazolyl-methane rhodium complex, preparation, 7, 185 Bis(pyrazolyl)methanes, in platinum(II) complexes, 8, 503 Bis(3-pyrazolyl)nickel complexes, preparation, 8, 80-81 Bis(2-pyridyl)amines... 

Diazoalkane addition to cyclopropenes having electron withdrawing substituents at 1- or 2-positions generally leads to the regioselectivity predicted on electronic or frontier orbital grounds ... 

The intermolecular addition of a carbene to a cyclopropene to give a bicyclo-[l.l.OJbutane is not a viable synthetic method since products of ring cleavage are usually observed However, diazoalkane addition to a cyclopropene (or bis-addition to an alkyne) is known to occur and subsequent deazetation generally leads to bicyclobutane and diene by separate pathways. 

The addition of diazoalkanes to a, -unsaturated esters provided some of the earliest examples of the 4,5-dihydro-3//-pyrazole route to cyclopropanes. For example, the addition of diazomethane to methyl 2-methyl-prop-2-enoate followed by thermal deazetization gave methyl 1-methylcyclopropane-l-carboxylate (5) in 63% overall yield (Houben-Weyl, Vol. 4/3, p47). This reaction is particularly favorable since the double bond is activated to diazoalkane addition... 

In some of these reactions, control of stereochemistry is critical and it is fortunate that for protected amino acid precursors, photochemical deazetization of the 4,5-dihydro-3//-pyrazole proceeds with high retention of stereochemistry. Hence, in the synthesis of the amino acid 12, the initial diazoalkane addition gave only one isomer (probably with the stereochemistry shown) and, although thermolysis gave a mixture of stereoisomers, photolysis gave the cyclopropane with the required trans configuration. 

There are few syntheses where imino-substituted cyclopropanes have been made by the diazoalkane addition route. One example is, however, provided by the synthesis of 7-(4-chloro-phenyl)-4-morpholino-5-oxa-6-azaspiro[2.4]hept-6-ene (33). ... 

In the case of enynes, there is competition between diazoalkane addition to the double bond (giving an ethynylcyclopropane) and addition to the triple bond (giving a pyrazole), and the balance between these two reactions is easily tipped in one or the other sense. Hence diphenyl-diazomethane and diazofluorene underwent addition to butenyne to give a good yield of the cyclopropane the intermediate 4,5-dihydro-3//-pyrazoles eliminating nitrogen even at room temperature, e.g. formation of 42. In the case of 2-methylbut-l-en-3-yne, however, only the pyrazole 43 was formed. ... 

The involvement of trimethylenemethane diradicals in deazetization of diazoalkane-allene adducts or trimethylene diradicals in the deazetization of the adducts of acyclic alkenes often leads to mixture of regioisomers and stereoisomers and from the standpoint of cyclopropane syntheses, this is undesirable. Far fewer problems of this type attend deazetization of the adducts of cyclic or polycyclic alkenes and, furthermore, even a modest amount of strain in the system activates the alkene to diazoalkane addition so that there is no need for activating substituents on the double bond. Cyclopropene is highly reactive towards diazoalkanes (see also Section 1.1.5.1.5.3.1.) and cycloaddition reactions of this type provide a ready entry into the bi-cyclo[1.1.0]butane series. The addition of diphenyldiazomethane to cyclopropene gave 4,4-diphenyl-2,3-diazabicyclo[3.1.0]hex-2-ene (1), which on photolysis gave a mixture of 2,2-diphenylbicyclo[1.1.0]butane (2) and 1,1-diphenylbuta-l,3-diene (3). ... 

Cyclopentadiene is more reactive towards diazoalkanes. It undergoes addition of diazomethane (and diazoethane) and thermal or photochemical deazetization of the adduct to give bi-cyclo[3.1.0]hex-2-ene or 6-methylbicyclo[3.1.0]hex-2-ene in good yield.Polycyclic systems incorporating strained cyclopentene units also react rapidly with diazoalkanes and cyclo-propanations via this route are relatively easy. Hence the addition of diazomethane to benz-valene 13 gave an 83% yield of the 4,5-dihydro-3//-pyrazole, which on photolysis gave tetra-cyclo[4.1.0.0 ". 0 ]heptane (27%) similar reactions are known for many other diazoalkanes. Addition of diazoethane to norborn-2-ene (14a) and thermal or photochemical... 

In most of the cyclopropanations of cyclopentenes, however, the double bond is activated to diazoalkane addition by a substituent. In cases where this is an exocyclic ester or acetyl... 

The review of Stanovnik (1991) concentrates on diazoalkane additions to some nitrogen containing heteroaromatic systems, namely to monocyclic pyridazines, and to bicyclic and polycyclic azolo- and azinopyridazines with a bridgehead N atom. 

The reaction of thiocarbonyl compounds with diazoalkanes (alkyl, aryl substituted) frequently gives good to excellent yields of thiiranes. The mechanism may involve addition of a carbene across the thiocarbonyl group, especially in the presence of rhodium(II) acetate... 

Diazirine, fluoromethoxy-nitrogen extrusion, 7, 224 Diazirine, methylvinyl-rearrangement, 7, 221 Diazirines addition reactions to Grignard compounds, 7, 2 0 as carbene precursors, 7, 236 IR spectra, 7, 203 microwave spectrum, 7, 199 molecular spectra, 7, 202-204 nitrogen extrusion, 7, 223 NMR, 7, 202 photoconversion to diazoalkanes, 7, 234 photoisomerization, 7, 221 photolysis, 7, 225-227 quantum chemical investigations, 7, 197 reactions... 

The regiospecificity observed above for diazomethane addition is lost when other diazoalkanes are used, for example, dimethyldiazomethane s reaction with 1,1-difluoroallene [24] (equation 16)... 

It IS likely that the syn selectivity exhibited in cycloadditions of fluoroallene IS due to electrostatic interactions [23 25] As in the case of difluoroallene the reactions of fluoroallene with diazoalkanes and nitrile oxides are facile, but such reactions, other than that shown in equation 18, are neither regio nor stereospeutic [23, 25] Indeed, the addition of phenylnitrile oxide to fluoroallene occurs with preferential anti addition for both regioisomenc products (equation 20)... 

Pertluoroallene is also quite reactive in its additions to nitrones [20], diazoalkanes [20] and sydnones [19] With sydnones, the isolated product derives from a fluoride ion rearrangement of the primary adduct (equation 21)... 

Tnfluoromethyldiazomethane behaves as atypical diazoalkane in its additions to carbon-carbon multiple bonds [9] For example, its reactions with ethylene and... 

Another class of nucleophilic addition to iminium salts can be found in the addition of diazoalkanes. These are of great interest since they were known to add and then reaet further to form three-membered rings as in the case of C=S, C=0, and C=C functions 103). Leonard and Jann 104-106) found that treatment of iminium perchlorates with diazomethane and other diazoalkanes yielded aziridinium salts. Treatment of an iminium salt such as N-cyclohexylidinepyrrolidinium perchlorate (66) with diazomethane yielded a new product whose structure was established by spectral and chemical means to be 5-azoniadispiro[4.0.5.1]dodecane perchlorate (67). The UV spectrum was devoid of any absorption above... 

The addition of acylazides leads to less stable triazolines, which lose nitrogen and rearrange to N-acylamidines (607). The triazolines obtained from sulfonylazides have been found to follow a similar reaction course as well as a path leading to the generation of diazoalkanes rather than nitrogen (596,599,608,609). 

In the case of the reaction between 2-diazopropane and diphenyldiacetylene, the reverse (as compared with other diynes) orientation of addition of the first molecule of the diazo compound with a predominant formation of 4-phenylethynylpyrazole is observed. Therefore, it is noteworthy that whereas the regioselectivity of the addition of diazoalkanes to alkenes is well studied audits products have, as a rule, the structure been predicted with respect to electron effects, the problem of orientation... 

The radical and the anion, R-N2 and R-N2, derived (formally) from a diazonium ion by addition of one and two electrons respectively, are named as diazenyl ( radical at the end is not necessary ) and diazenide (IUPAC, 1993). The radical derived formally from a diazoalkane by addition of a hydrogen atom (R=N-NH) is named diazanyl . In order to be consistent with the nomenclature of diazonium ions, the name of the parent compound should precede the words mentioned, e. g., benzenediazenyl for C6H5 - NJ (the term phenyldiazenyl radical is, however, used by Chemical Abstracts). 

When diazo ketones are treated with HBr or HCl, they give the respective a-halo ketones, but HI does not give the reaction, since it reduces the product to a methyl ketone (10-87). a-Fluoro ketones can be prepared by addition of the diazo ketone to polyhydrogen fluoride-pyridine. This method is also successful for diazoalkanes. 

Diazoalkanes are u.seful is precursors to ruthenium and osmium alkylidene porphyrin complexes, and have also been investigated in iron porphyrin chemistry. In an attempt to prepare iron porphyrin carbene complexes containing an oxygen atom on the /(-carbon atom of the carbene, the reaction of the diazoketone PhC(0)C(Ni)CH3 with Fe(TpCIPP) was undertaken. A low spin, diamagnetic carbene complex formulated as Fe(TpCIPP)(=C(CH3)C(0)Ph) was identified by U V-visible and fI NMR spectroscopy and elemental analysis. Addition of CF3CO2H to this rapidly produced the protonated N-alkyl porphyrin, and Bit oxidation in the presence of sodium dithionitc gave the iron(II) N-alkyl porphyrin, both reactions evidence for Fe-to-N migration processes. ... 

Diazoalkanes add readily to the double bond of esters of vinylphosphonic acid, giving the pyrazoline derivatives (100), which can lose nitrogen to give esters of cyclopropylphosphonic acids. In a similar reaction, acyl-phosphonic acid esters (101) were converted to epoxy-derivatives (102). A -Phenylsydnone adds to diethyl prop-l-ynephosphonate, giving the pyra-zole (103). The addition of cyclopentadiene to dimethyl vinyl phosphate leads to an exojendo quotient of 1.2, but with hexachlorocyclopentadiene only e/ii/o-isomer is formed. ... 

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