Diazo compounds nucleophilic additions

Hexafluoroacetone azine accepts nucleophiles (ROH, RSH, R NH) in positions 1 and 2 to yield hydrazones [27] Phosphites give open-chain products via a skeletal rearrangement [22] Radical addition reactions are also reported [22] Treatment of tnfluoropyruvates with tosylhydrazine and phosphorus oxychlo-ride-pyndme yields tnfluoromethyl-substituted diazo compounds [24] (equation 3)... 

Although formally the product of 1,4-addition of the carbene to the ADC 4n unit, 1,3,4-oxadiazolines probably arise via initial nucleophilic attack of the diazo compound to give, after loss of N2, a dipolar intermediate. This intermediate azomethine imine can collapse directly to give the oxadiazoline,... 

When other acceptor systems such as tetracyanoethylene, ethyl propiolate, dibenzoylacetylene, or dimethyl azodicarboxylate were reacted with 41, no additional products were formed. Accordingly, the scope of the reaction for the nucleophilic addition of 41 to electron-poor alkenes, alkynes, and diazo compounds is quite narrow. 

A Sandmeyer reaction leading to the 3-chloro derivatives was observed upon treatment of 3-diazotriazoles with aqueous hydrochloric acid [1898LA33 26JCS1729 78ZN(B)216]. 3-Diazotriazole was reduced to the parent triazole by treatment at 0°C with primary and secondary alcohols [86DIS(B) (46) 3052]. The mechanism is not clear, but the process may be envisaged as involving hydride transfer from the intermediate 244 obtained by nucleophilic addition of alcohols to the diazo compound (Scheme 70). 

A statement made in an earlier review (5), that the synthetic potential of cycloadditions of diazo compounds with heterocumulenes does not appear to have been extensively probed, is still valid. This may be due in part to the complexity of the reaction. Instead of a concerted [3 + 2] cycloaddition, nucleophilic addition of the diazo compound at the heterocumulene can lead to a diazonium betaine from which several different products can arise with or without conservation of the azo moiety. 

A neutral diazo compound can be considered as both a nucleophile and an electrophile. Thus, it can be substituted by the combination of an electrophilic moiety and a nucleophilic moiety (X+ Nu ") (Scheme 8). In practice, the diazomethyl group is transformed to the fluoromethyl group by treatment with hydrogen fluoride/pyridine mixture (70 30 w/w) (X = H Nu = F), or to the halofluoromethyl group by addition of A-halosuccinimide in the same medium (X = Cl, Br, I Nu = F), e.g. formation of l.16 The reaction can be performed on secondary diazo alkanes, diazo ketones or diazo esters.16 90 316... 

The first step was development of a catalytic epoxidation cycle using stoichiometric amounts of achiral sulfides and rhodium acetate [212-214]. The nucleophilicity of the sulfide plays a key role. In addition, the absence of sulfides led to the formation of stilbenes, and homologated products were formed in the absence of rhodium acetate [214]. This emphasizes that the sulfide and the rhodium catalyst were required for the operation of the catalytic cycle shown in Scheme 6.87B [214], It was also found that the reaction proceeded to completion with catalytic amounts of the sulfide. A prerequisite is slow addition of the diazo compound over a longer period of time, e.g. 24 h, to avoid the assumed dimerization of the diazo compound as a competing reaction under those conditions [214, 215]. 

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). 

When radical anions and dianions leads to very slow SET, their nucleophilic properties have to be taken into account. Reactions of electrogenerated species toward CO2, acetic anhydride, acetic chloride, and some classic RX compounds as electrophiles can be explained on the basis of nucleophilic substitutions, but extreme cares have to be taken on the intrinsic nature of the mechanism (Sn vs. radical coupling). Thus reactions involving azo and diazo compounds in the presence of CO2 could be explained by nucleophilic addition (formation of A-functionalized azine and diazines [13]). Several reactions [15,215,229] implying CO2 and acetic anhydride [230] were described. 

This homologation reaction most likely proceeds via nucleophilic addition of the diazo compound to the Lewis acid complexed carbonyl, followed by 1,2-alkyl migration with concomitant loss of N2. Application of this reaction to an aldehyde (168) gives, via 1,2-hydride shift, the corresponding P-keto ester (169 equation 70). ... 

The nucleophilic addition of Ti(IV) enolates of a-diazo-p-ketones 136 and 126 to N-tosylimine 182 and 184 is successfully promoted by the activation of TiCU to give b-(N-tosyl)amino substituted p-keto diazo carbonyl compounds 183 and 185.83... 

Nucleophilic addition of Ti(IV)-enolates of diazo ketone (136) to cycloheptanone (186) affords alcohol 187 which, on further dehydration with trifluoroacetic anhydride gives a,P-unsaturated carbonyl compounds (188 189) in 58% yield.84... 

The 7t sulfuranes are isoelectronic with diazo compounds and therefore may be expected to possess very similar chemical reactivity. However, the zwitteridnic character of these intermediates is greater than that of diazo compounds thereby facilitating their nucleophilic additions to carbonyl groups and Michael acceptors such as a,p-unsaturated carbonyl systems. DiphenylsulfoniumallyMe serves as a typical example. ) Thus, it reacts with 4-f-butylcyclohexanone to give the epoxide with predominantly the trans configuration and with methyl acrylate to yield the cyclopropane after 1,3-elimination. Many new t5 es and new reactions of n... 

Diazo compounds react with cobalt(II)-porphyrins, including [Co (Pl)] to give complexed carbenes (Figure 4.12). These can then undergo carbonylation by addition of carbon monoxide, with in situ capture of the ketenes by nucleophiles, or with imines forming PTactams (Eqn (4.45)). ... 

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