P-Acetylenic alcohols

P-Acetylenic alcohols (11, 378). The propargyltitanium reagent derived from 1-trimethylsilyl-3-(tetrahydropyranyloxy)propyne (1) reacts with crotonaldehydes to afford the P-acetylenic alcohol 2 with high stereoselectivity. This alcohol was used in a stcr-eocontrolled synthesis of the natural antibiotic ( )-asperlin (6). 

P-acetylenic alcohols, ethers and amines but also with alkylacetylenes. With suitable reagents ring syntheses become possible, e.g. equation (198) -... 

The P-acetylenic alcohol, 3-hexyne-l-ol, also reacted with the P=N species via addition of the 0-H moiety. In this case, however, the next step is a simple proton migration from nitrogen to phosphorus to give the P-H bonded P isomer. Similar addition-migration processes are found in the reactions of the two-coordinate phosphinimine with simple aliphatic alcohols (5). 

Allenylzirconium reagents Cp2Zr reacts with propargylic ethers to form an allenylzirconium reagent (a) that reacts in situ with aldehydes in the presence of BFj etherate to form anti- -acetylenic alcohols as the major product. In addition to the syn-and anti-p-acetylenic alcohols, a significant amount of an a-allenic alcohol is usually formed. 

Selective oxidation of a,p-unsatutrated (allylic, benzylic, acetylenic) alcohols. 

In the flask were placed 1.50 mol of the isopropenyl ether (conmercially available) and 0.10 mol of the (dry) acetylenic alcohol (also commercially available), and in the dropping funnel 0.4 mol of the latter compound. The mixture was cooled to 0°C and 100 mg of anhydrous p-toluenesulfonic acid were added with stirring. 

Answer Amide disconnection gives chloroformate (7), made from alcohol (8) with COCl (cf p T37). Alcohol (8) is a simple acetylene adduct. 

The heterogeneous catalytic system iron phthalocyanine (7) immobilized on silica and tert-butyl hydroperoxide, TBHP, has been proposed for allylic oxidation reactions (10). This catalytic system has shown good activity in the oxidation of 2,3,6-trimethylphenol for the production of 1,4-trimethylbenzoquinone (yield > 80%), a vitamin E precursor (11), and in the oxidation of alkynes and propargylic alcohols to a,p-acetylenic ketones (yields > 60%) (12). A 43% yield of 2-cyclohexen-l-one was obtained (10) over the p-oxo dimeric form of iron tetrasulfophthalocyanine (7a) immobilized on silica using TBHP as oxidant and CH3CN as solvent however, the catalyst deactivated under reaction conditions. 

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. 

A synthetic method for the preparation of chiral a- and p-allenic alcohols starting with a chiral acetylenic amine 20 and involving an LAH reduction as a key step was reported by Claesson and Mosher (54). This is illustrated in Scheme 3. Based on the stereochemistry of 20 to 24, it can be deduced that the attack... 

The procedure described below is quite general and uses finely, freshly machine--powdered KOH, which is added to a solution of the primary or secondary (acetylenic) alcohol and a 10-15% molar excess of tosyl chloride in Et20, kept around 0 C The excess of tosyl chloride is destroyed during the reaction of the excess of KOH. Side- and subsequent reactions ("saponification of the ester by KOH and 1,2-elimination of p-toluenesulfonic acid from thtfester) can be suppressed by keeping the temperature of the reaction mixture below 5 C. This procedure can be carried out within 2 h and generally gives excellent (often almost quantitative) yields of the tosylates. Purification of acetylenic tosylates by distillation, which is risky because of the limited thermal stability of the esters, is not necessary because the... 

Cabarrocas G, Ventura M, Maestro M, Mahia J, Villalgordo JM (2001) Synthesis of novel optically pure quinolyl-P-amino alcohol derivatives from 2-amino thiophenol and chiral a-acetylenic ketones and their IBX-mediated oxidative cleavage to IV-Boc quinolyl carboxamides. Tetrahedron Asymmetry 12 1851-1863... 

RC = CCH,X — RCX = C==CH,. /S.y- and 7,S-Acetylenic alcohols can be transformed to the halides in better yields by an alternative procedure, which consists in their esterification with p-toluenesulfonyl chloride and subsequent cleavage of the ester by the action of sodium iodide, lithium chloride, or calcium bromide in an appropriate solvent (60-90%). Halo ethers are prepared by the action of phosphorus tribromide on hydroxy ethers, as in the preparation of /3-ethoxyethyl bromide (66%). In a similar manner, /3-halo esters have been prepared without appreciable dehydration of the /3-hydroxy ester (40-60%). The reaction of cyanohydrins leads to a-halo nitriles. Treatment of 2-nitro-l-propanol with phosphorus pentachloride gives l-chloro-2-nitropropane (47%). ... 

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... 

Me3Si)2NP=ESiMe3 (1 E = CH 2 E = N) with a diverse series of unsaturated organic substrates are reported. For example, phosphines 1 and 2 react readily with allenes via an ene process to afford novel phosphorus-substituted dienes or with 2-butyne to give allenic phosphines. Other derivative chemistry, including the addition of terminal acetylenes and acetylenic alcohols to the P=E bond as well as some related reactions with acetylenic halides and both P- and y-diketones, is also described. 

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. 

Geiparvarin (898) isolated from Geijera parviflora, reported to have antitumor properties, was first synthesized by Smith et al., who thereby also established the stereochemistry of the double bond. The synthesis consisted of the aldol addition of the aldehyde 899 (R = CH2CHO), prepared from umbelliferone (899, R = H), to 5-ethyl-2,2-dimethyl-2/f-furan-3-one (900) when both isomers of 898 were obtained, the ( )-isomer being identical to the natural product. The synthesis of Jackson and Raphael (Scheme 67) starts with the acetylenic alcohol 901, once readily available, but no longer, because of the hazards associated with its handling (cf. Vol. 4, p. 558, Ref. 733). The... 

Types of reactions we meet elsewhere in the book include the reduction of a,p-unsaturated carbonyl compounds prepared by the aldol or Wittig reactions. The cyclic enone 14, prepared by a Robinson annelation is reduced regio- and stereo-selectively by LiAlH4 to the allylic alcohol2 15. The reduction of acetylenic alcohols 16, prepared by addition of metallo-alkynes to aldehydes, also with LiAlH4 is -selective (chapter 15) giving the allylic alcohol3 -17. 

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