3- propylidene acetal

Diethylacetal 1 has been used to obtain various other acetals by transacetalization,6 14c such as the dimethyl, the ethyleneglycol, and the neopentylglycol acetal (2,2-dimethyl-1,3-propylidene acetal). 

A chiral titanium complex with 3-cinnamoyl-l,3-oxazolidin-2-one (2d) was isolated by Jorgensen et al. from a mixture of TiCl2(0-z-Pr)2 with (2R,3R)-2,3-0-isopropylidene-l,l,4,4-tetraphenyl-l,2,3,4-butanetetrol (1-Me) which is an iso-propylidene acetal analogue of 1 [35]. The structure of the complex was determined by X-ray methods. The complex consists of the isopropylidene diol 1-Me and the cinnamoyloxazolidinone 2d in the equatorial plane and the two chloride ligands in the apical (trans) position as depicted in structure A (Scheme 3). It appears from this structure that the pseudo-axial phenyl group of the chiral ligand seems to block one face of the coordinated 2d. In contrarst, from an NMR study of the complex in the solution, Di Mare et al. reported that the above trans... 

The application of gas-liquid chromatography td the analysis of nucleosides has been described, and the retention volumes of some nucleoside derivatives are given in Table XIII. Although the free nucleosides are not sufficiently volatile, derivatives in which the hydroxyl or amino groups had been blocked by combinations of acetylation, methylation, or iso-propylidene acetal formation could be eluted successfully. The peaks obtained were well defined and reproducible, although antisymmetrical. 

An apparatus for descending, thin-layer chromatography of iso-propylidene acetals of L-sorbose has been described. 

OL,, -Trinitro-Propionaldehyde methyl imide ( 03,7,7-Trinitro-Propyliden]-methyl-amine). CH3.N CH.CH(N02).CH(N02)2 mw 206.14 N 27.19% white crysts. V sol in acet si sol in w insol in eth. Prepn is by reacting a,j3 J3-trinitro-propionaldehyde suspended in ammonia with an excess of methylammonium chloride. The imide is recovered by acidifying the mixt with HC1... 

Linear [ ]-pol3turethane derived from 1-deoxy-l-isocyanate-2,3 4,5-di-(9-iso-propylidene-D-galactitol (prepared from 48) in the presence of TEA or Zr(acac)4, as well as its corresponding polyhydroxy derivative obtained by hydrolysis of the acetal protecting group, have been prepared [117]. They are semicrystalline materials that exhibit high melting temperatures and thermal stability up to 230°C. 

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. 

Chemical Name ll-((Z)-3-(Dimethylamino)propylidene)-6,ll-dihydrodibenz[b,e]oxepin-2-acetic acid... 

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... 

The use of cycloaddition reactions for the synthesis of partially reduced heterocyclic systems was shown to be an attractive approach to dihydrobenzimidazoles, dihydroquinazolines, and dihydro-//n-benzopurines (Scheme 14) <86JOC6i6>. The dihydroxylation of the Diels-Alder adduct dimethyl 3,6-dihydrophthalate (128) with 0s04 and NMO followed by protection of the diol as the iso-propylidene derivative afforded compound (129). Saponification, dehydration with ethoxyethyne, and rearrangement with TMS—N3 effected conversion to the substituted tetrahydroisatoic anhydride (130), and subsequent treatment with formamidine acetate yielded compound (131). The substituents at the 6,7-positions of compound (131) were not amenable, however, for annelation of an imidazole. 

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... 

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