Rearrangements acetylenic alcohols

The isophytol side chain can be synthesized from pseudoionone (Fig. 5) using chemistry similar to that used in the vitamin A synthesis (9). Hydrogenation of pseudoionone (20) yields hexahydropseudoionone (21) which can be reacted with a metal acetyUde to give the acetylenic alcohol (22). Rearrangement of the adduct of (22) with isopropenyknethyl ether yields, initially, the aHenic ketone (23) which is further transformed to the C g-ketone (24). After reduction of (24), the saturated ketone (25) is treated with a second mole of metal acetyUde. The acetylenic alcohol (26) formed is then partially hydrogenated to give isophytol (14). 

MEYER - SCHUSTER Propargyl alcohol rearrangement Add catalyzed rearrangement of acetylenic alcohols into o, -unsaturated carbonyl derivatives... 

Tlie addition reactions of allylic and acetylenic alcohols produce compounds resulting from rearrangements [16, 17] (equation 7). 

When X=OH, this conversion of acetylenic alcohols to unsaturated aldehydes or ketones is called the Meyer-Schuster rearrangement The propargyl rearrangement can also go the other way that is, 1-haloalkenes, treated with organocopper compounds, give alkynes. ... 

Petrov and coworkers [41] showed that the reaction of dibromides of alkenephos-phonic acids with acetylenic alcohols involved an acetylene-allene rearrangement. The products so formed hydrolyzed easily to the corresponding phosphinic acids. The latter on heterocyclization afforded 2,5-dihydro-l,2-oxaphosphole-2-oxide derivatives (Scheme 11). 

Boisselle, A.P. and Meinhardt, N.A., Acetylene-allene rearrangement reactions of trivalent phosphorus chlorides with a-acetylenic alcohols and glycols,. Org. Chem., 27, 1828, 1962. 

Cutting and Parsons described the transformation of acetylenic alcohols 314 into allenyl phenyl thioethers 316 by a two-step procedure (Scheme 8.85) [174], Deprotonation of alkynes 314 with n-butyllithium is followed by addition of phenylsulfenyl chloride, forming sulfenyloxy intermediates which subsequently rearrange to allenic sulfoxides 315. Treatment of allenes 315 with methyllithium results in loss of the sulfoxide moiety to form allenyl sulfides 316 in reasonable yields. 

In the area of reaction energetics. Baker, Muir, and Andzehn have compared six levels of theory for the enthalpies of forward activation and reaction for 12 organic reactions the unimolecular rearrangements vinyl alcohol -> acetaldehyde, cyclobutene -> s-trans butadiene, s-cis butadiene s-trans butadiene, and cyclopropyl radical allyl radical the unimolecular decompositions tetrazine -> 2HCN -F N2 and trifluoromethanol -> carbonyl difluoride -F HF the bimolecular condensation reactions butadiene -F ethylene -> cyclohexene (the Diels-Alder reaction), methyl radical -F ethylene -> propyl radical, and methyl radical -F formaldehyde -> ethoxyl radical and the bimolecular exchange reactions FO -F H2 FOH -F H, HO -F H2 H2O -F H, and H -F acetylene H2 -F HC2. Their results are summarized in Table 8.3 (Reaction Set 1). One feature noted by these authors is... 

Rearrangements arc common in reactions of sulfur tetrafluoride with acetylenic and allylic alcohols. Highly acidic acetylenic alcohols derived from hexafluoroacetone and other haloacetones react readily at ambient temperature to give fluorinated allenes 10 as the sole... 

Chiral allenes. A key step in a recent synthesis of the optically active pheromone of the male boll weevil (3) used the orthocstcr Claisen rearrangement for transfer of the chirality of the acetylenic alcohol 1 to the allene 2. The final product (3) shows a higher optical rotation than the naturally occurring material, which may... 

MEYKR-SCHUSTER REARRANGEMENT. Acid catalyzed rear rangement of secondary and tertiary a-acetylenic alcohols to a.ft-unsaiurated carbonyl compounds aldehydes when the acetylenic group is terminal, ketones when it is internal. 

The acetylenic alcohol 2 can be converted into the Ouoridc 3 via the trimethylsilyl ether without rearrangement, which is also the expected reaction for the underivatized alcohol 2. ... 

The method has been extended to the preparation of difunctional compounds. Dihalides Including the mixed variety are formed in 90 to 98% yields. Primary unsaturated bromides of the type RCH=CHCH,Br have been formed from the corresponding alcohols by the action of phosphorus tribromide and pyridine at a low temperature without any apparent rearrangement. However, the corresponding secondary-carbinol system, RCHOHCH=CH is very susceptible to allylic isomerization. The formation of a, -acetylenic bromides from acetylenic alcohols and phosphorus tribromide is common (40-70%). An acetylenic-allenic isomerization has been observed, viz.,... 

The acid catalyzed rearrangement of tertiary acetylenic alcohols, the Rupe reaction, is a viable procedure for the preparation of a,p-unsaturated carbonyl compounds. Under standard acidic conditions, however, the products can polymerize and various by-products can be produced. With solid acids these problems are minimized. The reaction of an acetylenic tertiary alcohol with Nafion-H gave the a,P-unsaturated ketone in good to very good yields (Eqns. 22.24—25). When this reaction was run using a vanadium pillared... 

We also obtained interesting results in studying the reactivity of acetylenic alcohols with the two-coordinate phosphines (eq 9). Depending on the position of the OH group relative to the triple bond, different types of products are obtained. In all cases, however, the first step of the reaction is addition of the 0-H group to the P=N center to yield the three-coordinate phosphine. In the case of a-acetylenic alcohols, this addition is followed by a rapid acetylene-allene rearrangement and a... 

Cherbuliez, E., Jaccard, S., Prince, R., and Rabinowitz, J., Formation and transformation of esters. Part 57. Acids and acid chlorides of P(III) and a-acetylenic alcohols. Esterification with or without rearrangement, Helv. Chim. Acta, 48, 632, 1965. 

Acid catalyzed rearrangement of acetylenic alcohols into a,p-unsaturated carbonyl compounds, (see 1st edition). 

The homochiral acetylenic alcohol 2 [derived from ( )-4-benzyloxy-2-butenol by asymmetric Sharpless epoxidation via 2 in four steps] is transformed either to ( )-3 by treatment w ith lithium aluminum hydride or to (Z)-4 by hydrogenation with Lindlar catalyst. Simple Claisen or ortho ester rearrangement yield the same, but enantiomeric, products 5 and 6 with 85-90% ee288. 

Bis-acetylenic alcohol 1 undergoes a facile oxy-Cope rearrangement to afford mixtures of ( )-and (Z)-enynones. The latter compounds react further to give spiroannulated methylenecy-clopentenone 4 upon enolization and clectrocyclic ring closure1134. 

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