Diazoacetates tert-butyl diazoacetate

The diazo transfer reaction between p-toluenesulfonyl azide and active methylene compounds is a useful synthetic method for the preparation of a-diazo carbonyl compounds. However, the reaction of di-tert-butyl malonate and p-toluenesulfonyl azide to form di-tert-butyl diazomalonate proceeded to the extent of only 47% after 4 weeks with the usual procedure." The present procedure, which utilizes a two-phase medium and methyltri-n-octylammonium chloride (Aliquat 336) as phase-transfer catalyst, effects this same diazo transfer in 2 hours and has the additional advantage of avoiding the use of anhydrous solvents. This procedure has been employed for the preparation of diazoacetoacetates, diazoacetates, and diazomalonates (Table I). Ethyl and ten-butyl acetoacetate are converted to the corresponding a-diazoacetoacetates with saturated sodium carbonate as the aqueous phase. When aqueous sodium hydroxide is used with the acetoace-tates, the initially formed a-diazoacetoacetates undergo deacylation to the diazoacetates. Methyl esters are not suitable substrates, since they are too easily saponified under these conditions. 

Although the hazardous properties of di-tert-butyl diazomalo-nate are not known with certainty, it is reasonable to assume that they are similar to those of diazoacetic esters, which are considered to be moderate explosion hazards when heated. Contact with rough or metallic surfaces should be avoided. The submitter has routinely distilled 10-g. quantities of di-ferf-butyl diazomalonate under argon with no sign of decomposition. 

Functionalized silacyclobutanes 16 result from photochemical decomposition of [azido-, isocya-nato- and isothiocyanato-bis(tert-butyl)silyl]diazoacetates 15. They undergo a remarkably facile ring-expansion reaction to cyclic O-silyl ketene acetals 17 even at 60°C. 

Buten-l-yl diazoacetate, 2377 tert-Butyl diazoacetate, 2423 tert-Butyl 2-diazoacetoacetate, 3009 5-/er/-Butyl-3-diazo-3//-pyrazole, 2831 Cyanodiazoacetyl azide, 1346 5-Cyano-4-diazo-4//-l,2,3-triazole, 1345 Diazoacetaldehyde, 0710 Diazoacetonitrile, 0675 Diazoacetyl azide, 0679... 

Another versatile synthon for the preparation of fullerene derivatives with polar groups on the side chain is the l,2-(carboxymethano)[60]fullerene 123, which can be obtained either from the corresponding ethoxycarbonylmethyl carboxylate 124 or tert-butyl carboxylate 125, which themselves are accessible by the reaction of the corresponding diazoacetate with Cjq (Scheme 4.26) [113],... 

The cycloadduct obtained from ethyl diazoacetate and the cyclic phosphaalkene 9-ferf-butyl-1,3-diphenyl- 10-phospha-1,3-etheno- 17/-benzopyran-4(37/)-one underwent spontaneous [3-1-2] cycloreversion and produced ethyl 5-tert-butyl-1,2,4-diazaphosphole-3-carboxylate (163). Still another transformation was found for P-trimethylsilyl-substituted diazaphospholes system 94, which suffered dediazonia-tion under the cycloaddition conditions and yielded phosphaalkene 95 (162) (Scheme 8.22). It was proposed that N2 extrusion and SiMe3 migration occur in concert. On the other hand, the cycloaddition products derived from phosphaalkene 93 and 2,2-dimethyl-1-diazopropane or diazo(trimethylsilyl)methane simply underwent tautomerization to the corresponding A -phosphapyrazoline (162) (94, R = f-Bu H shift R = SiMe3 SiMe3 shift). 

Katsuki has recently constructed a series of chiral Co(III)-salen complexes 30 and used them as catalysts for cyclopropanation of styrene using tert-butyl diazoacetate [78], Not only is enantiocontrol for addition greater than 90% ee, but diastereoselectivity favors the trans-... 

The group of Arai and Nishida investigated the catalytic asymmetric aldol reaction between tert-butyl diazoacetate and various aldehydes under phase-transfer conditions with chiral quaternary ammonium chloride 4c as a catalyst. The reactions were found to proceed smoothly in toluene, even at —40°C, when using 50% RbOH aqueous solution as a base, giving rise to the desired aldol adducts 23 with good enantioselectivities. The resulting 23 can be stereoselectively transformed into the corresponding syn- or anti-P-hydroxy-a-amino acid derivatives (Scheme 2.20) [42],... 

A dry test tube containing catalyst (1.4 mg, 2 pmol, 2 mol%) and the imine (44.4 mg, 0.15 mmol, 1.5 equiv) was purged with nitrogen and then charged with toluene (1 mL). The resulting solution was treated with neat tert-butyl diazoacetate (14.2 mg, 0.1 mmol, 1 equiv) at r.t. After stirring for 24 h at ambient temperature, the mixture was subjected directly to FC on silica gel (hexanes ethyl acetate, 10 1 to 3 1) to give the product (32.9 mg, 75 pmol, 75% yield, 95% ee) as an oil. 

The substitution pattern in the product obtained through this sequence was in agreement with the proposed mechanism (Table 3.7). For example, crotyl chloride gave the 2-chloro-3-methyl hex-4-enoates (entries 3 and 4), and propargyl bromides gave the allenic products (e.g., entries 7 and 8). Yields were usually better with the more substituted tert -butyl diazoacetate. 

Diazoacetic acid silyl esters can be prepared by fra t-esterification of tert-butyl diazoacetate with trialkylsilyl triflate <1985JOM33>. Analogously prepared (alkenyloxy)silyl 203 and (alkynyloxy)silyl diazoacetates 206 underwent silicon-tethered 1,3-dipolar cycloaddition reactions as shown in Scheme 37 and Equation (38). Compound 205 resulted from a lateral criss-cross cycloaddition of the intermediate azine 204, which was formed from two molecules of 203 by diazo + diazo or diazo + carbene reaction <2000T4139>. On the other hand, when silyl diazoacetates 206 were kept in xylene at 142 °C for 1 h, bicyclic pyrazoles 207 were obtained (Equation 38). 

Dirhodium(ll) tetrakis[methyl 2-pyrrolidone-5(R)-oarboxylate], Rh2(5R-MEPV)4, and its enantiomer, Rh2(5S-MEPY)4, which is prepared by the same procedure, are highly enantioselective catalysts for intramolecular cyclopropanation of allylic diazoacetates (65->94% ee) and homoallylic diazoacetates (71-90% ee),7 8 intermolecular carbon-hydrogen insertion reactions of 2-alkoxyethyl diazoacetates (57-91% ee)9 and N-alkyl-N-(tert-butyl)diazoacetamides (58-73% ee),10 Intermolecular cyclopropenation ot alkynes with ethyl diazoacetate (54-69% ee) or menthyl diazoacetates (77-98% diastereomeric excess, de),11 and intermolecular cyclopropanation of alkenes with menthyl diazoacetate (60-91% de for the cis isomer, 47-65% de for the trans isomer).12 Their use in <1.0 mol % in dichloromethane solvent effects complete reaction of the diazo ester and provides the carbenoid product in 43-88% yield. The same general method used for the preparation of Rh2(5R-MEPY)4 was employed for the synthesis of their isopropyl7 and neopentyl9 ester analogs. 

Aryl-5,5-bis(oxazolin-2-yl)-l,3-dioxanes 169 have been easily prepared in three steps from diethyl bis(hydroxymethyl)malonate, amino alcohols, and aromatic aldehydes. They have been used for the copper-catalyzed asymmetric cyclopropanation of styrene with ethyl diazoacetate in up to 99% ee for the trawx-cyclopropane (maximum transicis ratio = 77/23) <05TA1415>. The same reaction performed on 2,5-dimethyl-2,4-hexadiene with tert-butyl diazoacetate in the presence of copper catalysts bearing ligand 170, prepared from arylglycines, exhibited remarkable enhancement of the rrawx-selectivity (transicis ratio = 87/13), with 96% ee for the trans product <05JOC3292>. 

Ishitani and Achiwa [16] have recently prepared an axially disymmetric rhodium (11) biphenylcarboxylate catalyst, Rh2(S-BDME)4 of Fig. 2, and found that although the transxis diastereoselectivity in its catalysis of the styrene-EDA reaction was poor, the enantiocontrol was better than that observed with the pro-linate catalyst. The biphenyl based catalyst yielded an 87% ee for the cyclopro-panation of 2-naphthylethene and tert-butyl diazoacetate, though again the diastereoselectivity was very low. Use of an additional chiral auxiliary in the diazoester as in the d-menthyl derivative in Eq. (10) furnished a mixture of cyclopropanes, the cis-isomer of which was found to have an ee of 99%. 

The ruthenium(ll) complex 20175c,d and the cobalt complexes 21179a and 22197b are also able to produce remarkable enantioselectivities in intermolecular cyclopropanation reactions. For the cyclopropanation of styrene with alkyl diazoacetates, the following ee-values have been reported 20 /t/V-buty , 94% (trans), 85% (cis), /-menthyl, 95% (as), 76% (trans), /-menthyl, 86% (cis), 95% (trans) 21 ethyl, 75% (cis), 20% (trans) 22 tert-butyl, 73% (trans). It is interesting to note that a catalyst analogous to 20, but with copper(II) triflate instead of ruthenium, displayed only low enantiocontrol.220b... 

Allyl methyl ether292 (ethyl diazoacetate, rhodium catalysis) and allyl tert-butyl ether124 (dimethyl diazomalonate, copper catalysis) yield cyclopropanes exclusively. With y-substituted allyl methyl ethers, C-0 insertion is generally strongly favored over cyclopropanation, even with tetraacetatodirhodium as catalyst.293 In view of these findings, the cyclopropanation of ( )- ,4-dibenzyloxybut-2-ene in moderate yield, only, to give (la,2a,3/ )-31 is notable.294... 

In 2004, Hossain and Redlich reported the synthesis of a series of iron-pybox complexes and their employment in the catalytic asymmetric aziridine forming reaction with imine (109a) and ethyl diazoacetate (10) (Scheme 16.31) [35]. When combined with AgSbFe, the isopropyl- and tert-butyl-pybox complexes (112a) and (112b) produce 47% of the cis-aziridine (110) in moderate enantiomeric excesses. The best overall results came when the tert-butyl pybox catalyst was used, although results obtained with the isopropyl pybox catalyst are very similar. 

Subsequently, Maruoka group developed an enantioselective 1,3-dipolar cycloaddition reaction between diazoacetates and a-substituted acroleins (Scheme 1.20) [24d]. The reactions of 1.5 equivalent of ethyl or tert-butyl diazoacetate and various a-substituted acrolein derivatives afford chiral 2-pyrazolines with high... 

In additimi to EDA, a more bulky diazo reagent, tert-butyl diazoacetate (t-BDA), was found to be suitable for the catalytic system, generating the corresponding tert-butyl a, -unsaturated esters 21 with comparable yields (73-94%) and E-selectivity (E/Z 62/38-99/1) (1) ... 

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