2- -2-alkene-1,4-diol 2-alkyn

Oxidation of alkenes and alkynes—sometimes with oxidative breakage of the carbon-carbon multiple bond—affording 1,2-diols,46,47 a-hydroxyketones 46 diketones,46 aldehydes,311,46 ketones46 or carboxylic acids31,44,46,29... 

The relevant literature in this subfield is too voluminous to be detailed here. Overviews are available [62], and only a few recent references to the newest publications are given below. Oxidations of the following types have been performed alcohol - ketone [63] aldehyde —> acid alkene —> diol or epoxide [64-67] al-kene - aldehyde, acid 1-alkyne —> ketoaldehyde and acid (1 C-atom shorter) internal alkyne —> a,/3-epoxyketone vic-diol —> 1,2-diketone [68] or hydroxyketone [69] amine —> amine oxide [70] aromatic amine —> nitrosobenzene, nitrobenzene, azoxybenzene [71]. 

Isopropoxy-4/f-l,3,2-benzodioxaborin (18) has been synthesized and found to react with a variety of hydroxy compounds to replace the isopropoxy group on boron. Aryl boric acids, RB(OH)2, reportedly condense with diols of the type HO(CH a)nOH to yield oligomeric rings (19) of varying size. The reaction of allenyl borates (20) with hydrogen bromide to yield alkenes and alkynes has been published. ... 

Heteropoly acids can be synergistically combined with phase-transfer catalysis in the so-called Ishii-Venturello chemistry for oxidation reactions such as oxidation of alcohols, allyl alcohols, alkenes, alkynes, P-unsaturated acids, vic-diols, phenol, and amines with hydrogen peroxide (Mizuno et al., 1994). Recent examples include the epoxidations of alkyl undecylenates (Yadav and Satoskar, 1997) and. styrene (Yadav and Pujari, 2000). 

Hydroboration of alkynes is easier to achieve than B-H addition to alkenes. A mixture of alcohol, ketone, and diol products is produced upon [Rh(PPh3)3Cl] catalyzed hydroboration of... 

Acetylenic precursors employed in the syntheses of sugars may be divided into three groups (a) aldehydes (usually in the form of acetals), (b) alkyl alkynyl ethers, and (c) alkynols or alkynediols. Some of them are commercially available (for example, 2-butyne-l,4-diol), and others are prepared by Grignard-type reactions between 1-alkynylmag-nesium halides or lithium alkynes and suitable aldehydes, ketones, or epoxides. In this way, the synthesis of substrates having the desired number of carbon atoms, as well as the necessary functional groups, can be achieved. The next step consists in partial saturation of the triple bond to afford the desired cis- or trans-alkene. ct.s-Alkene systems... 

Intramolecular geometries, database studies, 1, 597 Intramolecular hydroalkoxylation, and etherification, 10, 672 Intramolecular pinacol coupling to cyclic 1,2-diols, 11, 51 with samarium reagents, 11, 60 Intramolecular silylformylation, alkynes and alkenes, 11, 489 Intramolecular solvomercuration alkenes, 2, 436 alkynes, 2, 439... 

Indeed only alkynes could be reduced in (CH3)4N+ solutions while alkenes were inactive. Reduction of 1-hexyne, propargyl alcohol and 1,4-butyne diol were performed 13 at a mercury cathode with (CH3)4NC1 as the electrolyte. The corresponding olefins were formed and the respective yields were 45 %, 62 % and 82 %. The diacetate of 15 behaved similarly. However only the trans isomer 16 was formed from 15 while a mixture of trans and cis (6 4) isomers resulted from the reduction of the diacetate. Polarography of several alkynes in methanol with (C4H9)4N+ electrolytes showed, 3) that they react close to background decomposition. It was therefore proposed 14) that (CH3)4N+-mercury may be involved in the cathodic reduction of alkynes when (CH3)4N+ salts serve as the electrolytes. 

Oxo ester complexes with nitrogenous bases (L). Although most of these species contain the osmyl unit there are so many of them that it is appropriate to deal with them in a separate reaction. Most of the complexes have an Os L ratio of 1 2 (the majority taking the form 0s02(02R)py2) and so we consider such species first and include those complexes of the type 0s02(02R)(L—L), where L —L is a bidentate N donor (usually 2,2 -bipyridyl). Within this first section we consider first the species derived from alkenes R or diols R(OH)2, viz. 0s02(02R)L2 or 0s02(02R)L—L, and then species derived from dienes, trienes and alkynes. We then deal with the much smaller body of complexes where the Os L ratio is 1 1. 

Aldehydes, RCHO (Sec. 7.9) (Sec. 7.9) (Sec. 8.4) (Sec. 17.7, 19.2) (Sec. 19.2, 21.6) from disubstituted alkenes by ozonolysis from 1,2-diols by cleavage with sodium periodate from terminal alkynes by hydroboration followed by oxidation from primary alcohols by oxidation from esters by reduction with DIB AH [HA1(i-Bu)2]... 

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