Diazomethane, reaction with allyl

Crotyl diazoacetate has been prepared by the procedure described here and by the reaction of diazomethane with crotyl chloroformate. The lower homolog, allyl diazoacetate, has been )repared by the reaction of allyl glycinate with nitrous acid and by the successive conversion of allyl chloroacetate to the corresponding azide, iminophosphorane, and, finally, the diazo ester. ... 

Selective reduction of 530 with DIBAL gave a mixture (1 3) of the allylic alcohols 531 and 532 via preferential delivery of hydride to the unsaturated carbonyl function from the exo face. The allylic alcohol 531 was then converted to the allylic ether 533 by reaction with diazomethane in the presence of anhydrous aluminum chloride, whereas the major allylic alcohol 532 was converted to... 

Phosphoryl diazomethanes react with 2,6-di-/erf-butylthiopyrylium ion (26) in the presence of triethylamine to give the corresponding 4-(di-azomethyl)-4//-thiopyrans 349-353. Reaction of compound 349 or 350 with di-/x-chlorobis-(7r-allyl)palladium(Il), instead of the expected thiepine derivative, afforded the anhydrobase 354 or 355, respectively (85T811). 

Palladium-catalyzed methylene transfer from diazomethane has proved effective for the cyclopropanation of 1-alkenylboronic acid esters allylic alcohols and amines 1-oxy-l,3-butadienes and allenes " Readily accessible iron complex (CO)2FeCH2S Me2 BF4 35 undergoes direct reaction with a range of alkenes to give cyclopropanes (equation 67) The salt is sensitive to steric effects and the reaction proceeds... 

Compared with results obtained for ethyl diazoacetate, reactions of diazomethane with allyl bromide produce a dramatic reversal in the relative reactivities of the carbenoid species towards the nucleophilic bromide and the carbon-carbon double bond. These results are in accord with a greater electrophilic selectivity of the dialkoxycarbonyl carbenoid intermediate relative to the ethoxycarbonyl carbenoid. That increasing the electrophilicity of the carbenoid intermediate can reverse its reactivity towards the nucleophilic heteroatom relative to the olefin is consistent with the nature of this... 

The (S)-lactone acid 1, obtained from L-glutamic acid by nitrous acid deamination, was converted to the acid chloride, then treated with excess diazomethane followed by hydrogen iodide to yield the keto-lactone 2. Amidation occurred quantitatively to give the partially racemized amide 3, which was purified by repeated recrystallizations. The vicinal diol resulting from reaction with excess methylmagnesium iodide was protected as the acetonide 4. An isomeric mixture of olefins (Z , 26 74) was obtained from the subsequent Wittig reaction. Reduction followed by separation on silver nitrate coated silica gel gave the (Z)-and ( )-alcohols in 20% (6) and 61% (5) yield, respectively. Conversion of the (S)-( )-alcohol (5) to the chloride then afforded the thioether (7) on reaction with sodium phenylsulfide. The thio ether anion was formed by treatment with n-butyllithium. Alkylation with the allylic chloride" (8), followed by removal of sulfur, then yielded the diene 9, which was converted in several steps to (/ ) (-t-)-10,11 -epoxy famesol. 

A more recent approach to 57 began with the Weiss-Cook reaction product 59. Trapping the enol tautomer of this compound with diazomethane preceded alkylation with allyl iodide and hydrolysis/ decarboxylation to generate 60. The final sequence of reactions involved ozonolysis, aldol cyclization, reduction, and dehydration afforded 57. 

The formation of D-glucaric acid by platinum-catalysed oxidation of D-gluconic acid has been noted in the previous section. Mono- and per-allyl ether derivatives of xylaric and galactaric acids have been prepared by treating the aldaric acid with allyl alcohol in the presence of an appropriate acid catalyst. Diallyl 3-0-allyl-2,4-0-methylenexylarate was obtained in good yield when 2,4-0-methylenexylaric acid reacted with allyl bromide in the presence of alkali. The reaction of 2,3,4-tri-O-acetylxylaryl dichloride with diazomethane has been mentioned in Chapter 7. 

The Simmons-Smith reaction " and its variants are widely used for the stereospecific synthesis of cyclopropane compounds. The methodology involves the use of copper-treated zinc metal (the zinc-copper couple) with diiodomethane to add methylene to a carbon-carbon double bond. Alternative use of diazomethane in catalytic reactions does not offer the same synthetic advantages and is usually avoided because of safety considerations. As significant as is the Simmons-Smith reaction for cyclopropane formation, its employment for organic synthesis was markedly advanced by the discovery that allylic and homoallylic hydroxyl groups accelerate and exert stereochemical control over cyclopropanation of alkenes (e.g, Eq. 21), and this acceleration has been explained by a transition state model... 

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]. 

Logothetis first reported that azirine (24a) reacts with diazomethane to produce the allyl azide (163).68 This reaction is postulated to proceed by a 1,3-dipolar cycloaddition to form the triazoline (162) which then undergoes a valence tautomerization to the allyl azide (163). 

Deprotonation of O-alkyl carbamates may be achieved in an enantioselective manner with s-BuLi-(-)-sparteine, and the most effective of these reactions employ the oxazolidinones 411. The related compounds 412 perform similarly, but have less neat NMR spectra. Enantioselective lithiation of 413, followed by carboxylation and methylation with diazomethane, generates the protected a-hydroxy acid 414 in >95% ee.176 Many other electrophiles perform well in the quench step, but not allylic or benzylic halides, which lead to partial racemisation.177 30... 

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