Phenyldiazomethanes

Tosyl azide reacts differently to give sulfonamide derivatives 134). The morpholine enamine from dibenzylketone (196) for instance reacted with tosylazide to give 197 and phenyldiazomethane (198), which was trapped with acetic acid giving benzyl acetate 134). 

The cycloaddition of thiirene dioxide with phenyldiazomethane gave 3,4,5-triphenylpyrazole (165a) and the acyclic a-diazobenzyl 1,2-diphenylvinyl sulfone (164a), both suggested to originate in the common 1,3-dipolar cycloaddition intermediate 1626 (equation 66). Diphenylthiirene dioxide reacts similarly with other diazoalkanes (161b-e). 

Interestingly, the cyclopropanation of styrenes with EDA catalyzed by the half sandwich iron complex [CpFe(CO)2(THF)] BF4 afforded cyclopropanes in good yields and with ds-selectivity cisitrans = 80 20) [62]. With phenyldiazomethane as a carbene source, excellent cA-selectivity (92-100%) was achieved (Scheme 15) [63]. 

In addition, this methodology was extended to the cyclopropanation of a series of alkenes with phenyldiazomethane, giving rise to the corresponding cyclopropanes with high yields, diastereo- and enantioselectivities, as shown in Scheme 6.9. It was shown that the diastereoselectivity of these reactions was not greatly altered by the type of rhodium carboxylate catalyst that was used. 

Phenyldiazomethane can also be used to introduce benzyl groups.184... 

With some 1,3-dipoles, two possible stereoisomers can be formed by syn addition. These result from two differing orientations of the reacting molecules that are analogous to the endo and exo TS in D-A reactions. Phenyldiazomethane, for example, can add to unsymmetrical dipolarophiles to give two diastereomers. 

Photolysis of phenyldiazomethane in cis- or trans-butene leads to nearly stereospecific cyclopropane formation, although some C—H insertion occurs<2W ... 

A singlet carbene was proposed to account for this stereoselectivity. Attempts to produce triplet carbene by collisional deactivation with octafluorocyclo-butane were unsuccessful and stereospecific addition to olefin still occurred. However, nonstereospecific addition to olefins and larger amounts of olefinic (insertion) products result from irradiation of the phenyldiazomethane in a frozen m-butene matrix at — 196°C ... 

The need for care in distillation of phenyldiazomethane is stressed. Previously it has been used as prepared in solution. 

As for cyclopropanation of alkenes with aryldiazomethanes, there seems to be only one report of a successful reaction with a group 9 transition metal catalyst Rh2(OAc)4 promotes phenylcyclopropane formation with phenyldiazomethane, but satisfactory yields are obtained only with vinyl ethers 4S) (Scheme 2). Cis- and trans-stilbene as well as benzalazine represent by-products of these reactions, and Rh2(OAc)4 has to be used in an unusually high concentration because the azine inhibits its catalytic activity. With most monosubstituted alkenes of Scheme 2, a preference for the Z-cyclopropane is observed similarly, -selectivity in cyclopropanation of cyclopentene is found. These selectivities are the exact opposite to those obtained in reactions of ethyl diazoacetate with the same olefins 45). Furthermore, they are temperature-dependent for example, the cisjtrcms ratio for l-ethoxy-2-phenylcyclopropane increases with decreasing temperature. 

The limitation to electron-rich alkenes in Rh(II)-catalyzed cyclopropanation with phenyldiazomethane leaves untouched the great versatility of zinc halides for this purpose with this, catalyst, efficient and very mild cyclopropanation of 1,3-dienes and unactivated alkenes has been reported 46). 

Aziridines have been synthesized, albeit in low yield, by copper-catalyzed decomposition of ethyl diazoacetate in the presence of an inline 260). It seems that such a carbenoid cyclopropanation reaction has not been realized with other diazo compounds. The recently described preparation of 1,2,3-trisubstituted aziridines by reaction of phenyldiazomethane with N-alkyl aldimines or ketimines in the presence of zinc iodide 261 > most certainly does not proceed through carbenoid intermediates rather, the metal salt serves to activate the imine to nucleophilic attack from the diazo carbon. Replacement of Znl2 by one of the traditional copper catalysts resulted in formation of imidazoline derivatives via an intermediate azomethine ylide261). 

It was also found that the ring expansion could be accomplished photo-chemically, from either phenyldiazomethane or triplet phenylcarbene.7 Both the thermal and photochemical ring expansions were found to be reversible,5c, thus providing rare examples of carbene-to-carbene interconversions. One remarkable example of this reversibility is the interconversion of the isomeric tolylcarbenes upon pyrolysis — the ultimate products of which include styrene and benzocyclobutene (Scheme 3).6,8,9... 

Phenyldiazomethane, 2725 Poly(diazomethylenemercury), 0522 Sodium diazomethanide, 0383 Tetrachlorodiazocyclopentadiene, 1807 2,2,2-Trifluorodiazoethane, 0664 See or-DIAZO- -OXOSULFONES, DIAZOMETHANE SALTS... 

Another paper64, which also contains a literature survey about the problem discussed, describes the rearrangements of C7H6 systems which can be generated by thermolysis of phenyldiazomethane. By using spectral methods and chemical reactions, the formation of bicyclo[4.1.0]hepta-2,4,6-triene (139), cycloheptatrienylidene (137a) and bicyclo[3.2.0] hepta-l,3,6-triene (135) was excluded, and evidence for the formation of intermediate cycloheptatetraene (137b) (see equation 45) was furnished. 

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