Aldehyde from 1,2-diols

An intramolecular cycloaddition reaction is also a vital feature of Oppolzer s synthesis (Scheme 5).336 Here the cycloaddition reaction occurs on an unsaturated nitrone ester (39) (not isolated). Again, the aldehyde derived from oxidation of the diol (40) gave entirely the ( )-olefin on reaction with crystalline a-methoxy-carbonylethylidenetriphenylphosphorane, which allowed the synthesis of (+)-chanoclavine I (34) to be completed in an overall yield of 14% from indole-4-aldehyde. In contrast, the Horner-Emmons reaction on the aldehyde from... 

Carbohydrates. Mild oxidants such as chlorine, bromine, or iodine readily convert the aldehyde end groups in the wood polysaccharides to aldonic acid end groups. Nitrogen dioxide selectively converts the primary hydroxyl groups on C-6 in cellulose to carboxyl groups (J3). Periodic acid is a specific oxidant for vicinal diols and yields formaldehyde from primary hydroxyl groups and aldehydes from secondary. 

Other titanium complexes derived from tartaric acid have been used as chiral catalysts. The complexes generated from diol 2.50 and TiCl2(0/-Pr)2 are used as catalysts in asymmetric ene-reactions [778, 816], and in Diels-Alder [778, 780] or [2+2] cycloadditions of ketene thioacetals and unsaturated sulfides [778, 817], The best enantiomeric excesses are observed with 2.50 (R = Me, R = Ph) [778, 817] or 2.50 (R = R = Et, Ar = 3,5-Me2CgH3) [45], These catalysts are also efficient in hydrophosphonylation [818] and in asymmetric hydrocyanation of aldehydes with Me3SiCN [778], These titanium complexes may be used in catalytic amounts provided that the reactions are run in the presence of molecular sieves [559,816],... 

Dimethylandrostane-6a,17/ -diol refluxed 2 hrs. in a dry suspension of excess Ag-carbonate-on-Celite in benzene 4,4-dimethyl-17-ketoandrostan-6a-ol. Y 87.5%. - Sterically hindered hydroxyl groups are not oxidized. F. e., also aldehydes from prim, alcohols, s. M. Fetizon and M. Golfier, C. r. 267 (C), 900 (1968) Chem. Commun. 1969, 1102. 

Cyclic acetals and ketals are normally prepared from diols, triols and polyhydroxy compounds by reaction with an aldehyde or ketone, and a wide variety have been used (see Table 2). 

Hydroboration of alkynes leads to an enol after treatment with NaOH/HgOg, and tautomerization gives an aldehyde from terminal alkynes, or a ketone from internal alkynes 44, 78, 83. Dilute potassium permanganate and osmium tetroxide react with alkenes to give a manganate ester or an osmate ester, respectively. Both of these products are decomposed under the reaction conditions to give a vicinal (l,2)-cis-diol 49, 50, 83, 96. 

RuH2(PPh3)4 is used as a dehydrogenation type oxidation catalyst for alcohols and aldehydes [66a,66b]. For example, the esterification of alcohol, lactone formation from diol, N-alkylation of amine with alcohol, and the condensation of aldehyde with alcohol. 

The initial step of the PAT/KOH/PAS reaction generates aldehydes from the Q, C7, and C9 classes of sialic acids and from tissue diols unassociated with sialic acid residues. Such aldehydes are stained blue with a Schiff reagent prepared from the phenothiazine dye, thionine. The subsequent saponification step removes acetyl groups from the Q class of sialic acids which are then stained red by the standard PAS procedure. Sites containing mixtures of these components stain in various shades of purple. As will be seen in Fig. 4, tissue sites which stain blue in the PAT/KOH/PAS procedure and red (positive) with the PBT/KOH/PAS technique are considered to contain the C7 class of sialit acids we have identified a predominance of such acids in a small number of tumours (Culling et al. 1977 a). 

A double reductive amination was one of several approaches used to build macrocycles from diol precursors or their electrophilic derivatives (aldehydes, halides) described by Clausen (Figure 11.18, sites of reaction indi-cated). ° Specifically, reaction of the bis-functionalized substrates with appropriate diactivated reagents were utilized to form cyclic carbonates (231), sulphites (232), phosphates (233), sulphides (234), amines (235, 236) and malonates (237) with ring sizes of 15-19 members. Although yields were... 

Diols that bear two hydroxyl groups m a 1 2 or 1 3 relationship to each other yield cyclic acetals on reaction with either aldehydes or ketones The five membered cyclic acetals derived from ethylene glycol (12 ethanediol) are the most commonly encoun tered examples Often the position of equilibrium is made more favorable by removing the water formed m the reaction by azeotropic distillation with benzene or toluene... 

Oxidation. Olefins in general can be oxidized by a variety of reagents ranging from oxygen itself to ozone (qv), hydroperoxides, nitric acid (qv), etc. In some sequences, oxidation is carried out to create a stable product such as 1,2-diols or glycols, aldehydes, ketones, or carboxyUc acids. In other... 

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