Propylidene, hydrogenation

On the other hand, severe congestion and a lower temperature (20°C) prevent the hydrogenation of the propylidene double bond (tetrasubstituted but... 

This trimeric propylidene peroxide , formed from propanal and hydrogen peroxide, is an extremely explosive and friction-sensitive oil. 

Methods of Formation.—Only one method has been used for the synthesis of 3,5,6-trimethyl-D-glucose, which has not yet been prepared in crystalline form. The method, published in 1913 by Irvine and Scott,20 entails methylation of 1,2-isopropylidene-n-glucofuranose and hydrolysis with 0.5% hydrogen chloride in aqueous alcohol of the resultant 1,2-iso-propylidene-3,5,6-trimethyl-D-glucofuranose. Modifications introduced... 

An iridium(I) complex with the l,2-bis(tcrt-butylmethylphosphino)ethane (4) and tetrakis(3,5-bis(trifluoromethyl)phenyl)borate as the counter anion catalyzes the hydrogenation of several acyclic aromatic Ai-arylimines under atmospheric hydrogen pressure at room temperature, giving the desired chiral amines with high-to-excellent enantioselectivities (up to 99%, Fig. 6) [19]. The authors also tested (S )-BINAP (Fig. 1) and (/ )-Ph-PHOX (PHOX = 2-[2-(diphenylphosphino) phenyl]-4,5-dihydrooxazole) hgands with lower enantioselectivities [19]. Both steric and electronic properties of the ligand and the combination with the BArF anion are in the base of the efficacy of this catalytic system. On the other hand, attempted hydrogenations of Ai-(2,2,2-trifluoro-l-phenylethylidene)aniline and M-(l,2,2-trimethyl-propylidene)aniline under the same conditions resulted in... 

The addition of iodine trifluoroacetate (produced by reaction of iodine with silver trifluoroacetate) to unsaturated carbohydrates has been investigated.134 Treatment of 5,6-dideoxy-l,2-0-isopropylidene-a-D-xylo-hex-5-enofuranose (89) with silver trifluoroacetate and iodine in acetonitrile gave 3,6-anhydro-5-deoxy-5-iodo-l,2-0-iso-propylidene-a-D-gluco(and /3-L-ido)furanose (91) and 5-deoxy-5-iodo-l,2-0-isopropylidene-6-0-(trifluoroacetyl)-o -D-gluco(and/or /3-L-ido)-furanose (92), with the former preponderating. Component 91 was converted into 3,6-anhydro-5-deoxy-l,2-0-isopropylidene-a-D-xj/io-hexofuranose (94) by hydrogenation over Raney nickel (see also, Section III,3 p. 299), and component 92 was converted into 5-deoxy-l,2-0-isopropylidene-a-D-xy/o-hexofuranose (95) by treat-... 

The action of 1% methanolic hydrogen chloride on 1,2-O-iso-propylidene -3,5-di - O - p-tolylsulfonyl-D-xylofuranose (65) leads,81 after boiling for three hours under reflux, to 2,5-anhydro-3-0-p-tolylsulfonyl-D-xylose dimethyl acetal (66). The structure of 66 was demonstrated by conversion into the disulfonate 67 this was prepared independently from a 2,5-anhydro-D-xylose dialkyl dithio-acetal72 (48) by p-toluenesulfonylation followed by exchange of the acetal group in methanol in the presence of mercury salts. 

The acidic hydrogen atoms in the side chain of alkylpyridines may interfere with the formation of o-adducts. Thus 4-isopropylpyridine reacts with phenyllithium in THF to yield a mixture of the 2-adduct 90 and l-lithio-4-(2-propyliden)-l,4-dihydropyridine (91). However, alkyllithiums, such as BuLi, (-BuLi, and MeLi, mainly yield the related 2-adducts 92.136... 

Methyl-5-tosyl-L-arabofuranosides (a/3 mixture) (XXXI) on condensation with acetone containing hydrogen chloride gave the 1,2-iso-propylidene derivative (XXXII). Methylation gave 1,2-isopropylidene-3-methyl-5-tosyl-L-arabofuranose (XXXIII) from which the tosyl... 

Schmidt and Wernicke74 have described a synthesis of digitalose starting with D-fucose dibenzyl mercaptal, which on condensation with acetone yielded the 4,5-isopropylidene derivative (LXXIV). Elimination of the dibenzyl mercaptal residues with mercuric chloride and cadmium carbonate in methanol gave 4,5-isopropylidene-D-fucose dimethylacetal (LXXV), from which the 2-benzyl ether was obtained on treatment with sodium and benzyl chloride. Methylation produced 2-benzyl-3-methyl-4,5-iso-propylidene-D-fucose dimethyl acetal (LXXVI), from which the iso-propylidene group was eliminated on treatment with methanolic hydrogen chloride, which also effected glycopyranoside formation (LXXVII). The... 

Ohle118 obtained 1-methyl-D-fructose by methylating 2,3 4,5-diiso-propylidene-D-fructopyranose and then hydrolyzing the resulting crystalline 1-methyl derivative. Brigl and Widmaier m have prepared 1-methyl-D-fructose from dibenzylidene-D-fructose. An alternative method is described by Brauns and Frush142 who hydrolyzed crystalline 1-methyl-D-fructosyl fluoride 3,4,5-triacetate, obtained by methylation with methyl iodide-silver oxide of crystalline D-fructosyl fluoride 3,4,5-triacetate, which results from the action of anhydrous hydrogen fluoride on D-fructose 1,3,4,5-tetraacetate. 

Freifelder obtained an 82% yield of benzylhydrazine by hydrogenating a freshly prepared hydrazone over Pd-C in ethanol at 0.3 MPa H2 in less than 30 min.83 However, when the hydrazone was allowed to stand for several days to a week, the yield dropped to 45-48%. In the hydrogenation of phenylacetone hydrazone, Biel et al. observed that the formation of large amounts of jV,iV -bis(l -phenyl-2-propylidene)hydrazine took place when hydrogenation proceeded slowly and incompletely with such catalysts as Pd-C, rhodium, ruthenium, and platinum oxide, and with solvents such as alcohol, water, ethyl acetate, tetrahydrofuran, and dioxane. The A(A%disubstituted hydrazine was obtained when the hydrogenation proceeded slowly to completion, as over platinum oxide in aqueous acetic acid. With Raney Ni in ethanol, the azine and l-pheny-2-propylamine were formed almost exclusively. 1-Phenyl-2-propylhy-drazine was obtained in acceptable yields of 55-70% by use of platinum oxide or supported platinum in alcoholic acetic acid at a pressure of 13.8 MPa H2. The products obtained over platinum oxide in various conditions are summarized in eq. 8.40.78... 

From the field of sugar chemistry may be dted the conversion of r>,d-anhydro-l 2-0-iM >ropylid6Cie-ceHn.gluc08e (Eq 642) to 1,2-0 im-propylidene-6 >ziercapto-6-deoxy a-i -g)ucose on iroatment vritir aOra-Jine hydrogen sulfide,... 

Treatment of 1,2 5,6-di-O-isopropylidene-a-D-allofuranose with methanolic hydrogen chloride for 20 hours affords the methyl 2,3-0-isopropylidene- and 2,3 5,6-di-0-isopropylidene-/3-D-allofurano-sides 118 again, migration to a favorably disposed hydroxyl group occurs. Evans62 reported the rearrangement of methyl 4,6-0-iso-propylidene-a-D-altropyranoside to the 3,4-acetal in acetone-sulfuric acid. 

Addition of nitryl iodide to 3-0-acetyl-5,6-dideoxy-l,2-0-iso-propylidene-a-D-xylo-hex-5-enofuranose, followed by dehydroiodina-tion of the product with sodium hydrogen carbonate in refluxing benzene, furnished910 the same 5,6-unsaturated 6-nitro hexose derivative (182, see Section IV,2c, p. 127) that had been synthesized previously by sequential acetylation and dehydroacetylation of 88. Borohydride reduction of 182 gave910 5,6-dideoxy-l,2-0-isopropyl-idene-6-nitro-a-D-xt/lo-hexofuranose. 

Hydrolysis of the known 3,5-0-benzylidene-6-deoxy-l,2-0-iso-propylidene-a-D-xt/Zo-hex-5-enofuranose affords a route to the antibiotic sugar 6-deoxy-D-xy(o-hexos-5-ulose 143 the synthesis of 5-deoxy-l,2-0-isopropylidene-6-0-trityl-a-D-xt/(o-hex-5-enose (79, R = H, R = OTr) has been discussed further,144 and, on hydrogenation, the compound, affords crystalline 5-deoxy-l,2-0-isopropylidene-a-D-xy/o-hexose.145... 

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