Lithiated diazo compounds

Related Reagents. Triisopropylsilyldiazomethane can be similarly converted into its lithium derivative. Diazo compounds containing tin (R3SnCHN2) and germanium (R3GeCHN2) are also known, but have not been used in synthesis. Other lithiated diazo compounds are covered elsewhere, as are other lithiated silanes. 

An interesting Fe-catalyzed SN2 -like carbene insertion reaction using diazo compounds and allyl sulfides (the Doyle-Kirmse reaction) was reported by Carter and Van Vranken in 2000 [20], Various allyl thioethers were reacted with TMS-diazomethane in the presence of catalytic amounts of Fe(dppe)Cl2 to furnish the desired insertion products with moderate levels of stereocontrol [Equation (7.6), Scheme 7.14]. The products obtained serve as versatile synthons in organic chemistry, e.g. reductive desulfurization furnishes lithiated compounds that can be used in Peterson-type oleftnations to yield alkenes [Equation (7.7), Scheme 7.14] [21]. 

Bis(diisopropylamino)phosphanyl(trimethylsilyl)diazomethane 6, easily available by treatment of chlorobis(diisopropylamino)phosphane with lithiated diazo(trimethylsilyl)methane, provides upon flash thermolysis at 250"C the so-called stable carbene 7.38,39,40 behaves partly as a nucleophilic carbene and reacts only with electron-deficient alkenes such as methyl propenoate or diethyl fumarate under cyclopropanation." In the former case only the Z-isomer 8 is formed. Cyclopropane 9 is thermally unstable and is, therefore, oxidized in situ at the phosphorus atom with elemental sulfur to provide cyclopropane 10, Cyclopropanes 8 and 9 are also generated from the diazo compound 6 and the appropriate alkene by photolysis." ... 

The most versatile carbene precursors are a-diazocarbonyl compounds such as diazoacetic acid esters because they are readily prepared, easy to handle and much more stable than ordinary diazoalkanes [10,38]. Nevertheless, one should always be aware of the potential hazards of diazo compounds in general [39],but if the necessary precautions are taken, they can be safely handled even on an industrial scale [18]. The most frequently used reagent is commercially available ethyl diazoacetate. Besides a-diazocarbonyl reagents, diazomethane [40,41 ] and a y-diazoacrylate derivative [42] have been used in enantioselective Cu-cata-lyzed cyclopropanations but the scope of these reactions has not been studied systematically. It has been shown in certain cases that diazo compounds can be replaced by other carbene precursors such as iodonium ylides, sulfonium yUdes, or lithiated sulfones [8,43],but successful applications of these reagents in enantioselective Cu-catalyzed reactions have not been reported yet. 

Dihydro-2-isopropyl-3.6-dimethoxypyrazine, a bis(lactim)ether, is converted into the 5-di-azo compound 1 by lithiation and diazo group transfer. The intermediate diazo compound reacts at room temperature with olefins such as cyclohexene to produce the cyclopropane derivatives with excellent diastereoselectivity . The derivative from cyclohexene is hydrolyzed by acid treatment to give methyl 7-cv(cfo-aminobicyclo[4.1.0]hcptane-7-carboxylate. The bis(lac-tim)ether diazo compound 1 is also involved in an exceptional asymmetric [2 + 1J cycloaddition producing cnantiomerically pure cyclopropenc derivatives4. Thus, reactions of the diazo compound with monosubstituted alkynes afford the spiro compounds as one diastereomer. Hydrolytic removal of the auxiliary and protection of the amino group provides enantiomerically pure methyl l-amino-2-arylcyclopropene-l-carboxylates in moderate overall yield. 

A variety of ylides (e.g. 5) of arsenic, antimony and bismuth have been prepared under mild conditions via the reaction of diazo compounds with the appropriate three valent organometalloid. Schmidbaur s group continues to produce new ylide structures, for example (6).5 The lithiated aza-ylide (8) has been prepared directly from the parent... 

A versatile starting material for the preparation of compounds belonging to the second class of polymers is (19) (R = Br) via a lithiation step numerous compounds have been prepared (19) (R = PPh2) readily forms complexes with transition metal compounds. Reduction of (19) (R = NO2) gives (19) (R = NH2), that can be used in diazotization and subsequent diazo coupling reactions. Another application of (19) (R = NH2) involves Schiff base... 

Aldehydes (RCHO) react with 1-diazo-l-lithioacetone to give a-diazo- -hydroxyketones (48). These latter compounds can then be converted to P-diketones by the addition of rhodium(il) acetate a procedure which has been applied in the synthesis of -damascone. 1,6,6A -Trithiapentalene and a metal salt catalyse the lithiation of unactivated alkenes to alkenyl-lithiums by lithium metal, constituting a very useful method for preparing such compounds since in the past the preparation of alkenyl-lithiums from lithium metal has been confined to alkenes containing relatively acidic protons. Finally, the allenyl-lithium reagent (49) can be converted to various functionalized allenes by simple electrophiles. ... 

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