Propargylic alcohols tertiary

Efforts to tune the reactivity of rhodium catalysts by altering structure, solvent, and other factors have been pursued.49,493 50 Although there is (justifiably) much attention given to catalysts which provide /raor-addition processes, it is probably underappreciated that appropriate rhodium complexes, especially cationic phosphine complexes, can be very good and reliable catalysts for the formation of ( )-/3-silane products from a air-addition process. The possibilities and range of substrate tolerance are demonstrated by the two examples in Scheme 9. A very bulky tertiary propargylic alcohol as well as a simple linear alkyne provide excellent access to the CE)-/3-vinylsilane products.4 a 1 In order to achieve clean air-addition, cationic complexes have provided consistent results, since vinylmetal isomerization becomes less competitive for a cationic intermediate. Thus, halide-free systems with... 

Tertiary propargylic alcohols reacted with carbon monoxide in the presence of a cationic palladium(II) complex, [Pd(NCMe)2(PPh3)2](BF4)2, to afford mixtures of 2(5H)-furanones and 2,3-dienoic acids (Scheme 3.23). Control experiments demonstrated that the latter products were converted into the former quantitatively with a trace amount of acid [58],... 

Secondary and tertiary propargyl alcohols are directly converted to halo-allenes on reaction with concentrated aqueous hydrogen halides in the presence of the corresponding cuprous halide [60,72-73]. (See Table VII.) Better yields are obtained with hydrogen bromide. Hydrogen chloride yields chloroallene, propargyl chloride, and the chloro- 1,3-diene isomers (Eq. 60). 

Tertiary propargylic alcohols suffer a very easy fragmentation under the action of Fetizon s reagent.14... 

Diynes 6, which consist of a trimethylsilyl alkyne tethered to a tertiary propargyl alcohol, undergo ruthenium catalyzed cycloisomerization in aqueous acetone to form the dienone intermediate 7. Concomitant electrocyclization affords 2-trimethylsilyl-2-//-pyrans in high yield (Scheme 3) <2004OL4235>. 

Indium trichloride promotes catalytically the addition of alkynylstannanes to aldehydes (Table 25).42 Metallic indium also mediates the same Barbier-type coupling between alkynyl halides and aldehydes or ketones to give secondary or tertiary propargyl alcohols (Table 26). Secondary alcohols can be oxidized in situ according an Oppenauer process.395 Thus, alkynyl ketones have been prepared from aldehydes via an indium-mediated alkynylation reaction followed by an indium-mediated Oppenauer oxidation. They are also obtained via an indium-mediated alkynylation of the relevant acyl chlorides (Table 27).396... 

Resolution of Alcohols. Although not a well exploited use of brucine, a variety of secondary benzylic alcohols have been resolved by complexation and crystallization with brucine (eq 5). About a dozen alcohols were obtained in close to enantiomeric purity by this procedure. Also resolved by crystallization of their brucine inclusion complexes were a series of tertiary propargylic alcohols (eq 6). In this case, the enantiomer that does not crystallize with brucine can be obtained in almost complete optical purity from the mother liquors. 

The same results are observed by Tadema et al. [83)]. The anr/-1,3-substitution route is the normal stereochemical pathway for secondary propargylic sulfinates, whereas the syn-route is preferred if the ester is derived from tertiary propargylic alcohols. 

Trost, B.M., Maulide, N. and Rudd, M.T. (2009) Ruthenium-catalyzed crosscoupling of tertiary propargyl alcohols with co-alkynenitriles a regio- and stereoselective surrogate for an aldol condensation. Journal of the American Chemical Society, 131, 420-421. 

Acylation. BifOTf), is an effect tertiary propargylic alcohols are acetylau... 

Acylation. Bi(OTf)3 is an effective catalyst for acylation. Thus, in its presence tertiary propargylic alcohols are acetylated in good yields. 

P-Lactones. Vicinal cfj-dicarbonylation of tertiary propargyl alcohols is observed in the presence of Pdlj and KI under CO. 

Curiously, tertiary propargylic alcohols may be alkylated in preference to either axial or equatorial secondary alcohols, using sodium hydride in DMF (eq 3). ... 

As a typical intermolecular carbopalladation and termination, hydroarylation of alkynes are carried out extensively in the presence of HCO2H as a hydride source. Formation of regioisomers is observed in the reaction of asymmetric alkynes, and ratios depend on the nature of the substituents. High regioselectivity was observed in the reaction of the tertiary propargylic alcohol 14 to give 15 as a major product [5]. The (Z)-2-arylcinnamates 17, rather than 3-arylcinnamate 18, was obtained by the hydroarylation of methyl phenylpropiolate (16) [6]. 3-Substituled quinoline 21 was prepared by the regioselective hydroarylation of 19, followed by treatment of 20 with an acid without isolation [6]. 

Propargyl alcohols are less reactive than their esters. Carbonylation of the tertiary propargyl alcohol 68 at 95 °C under pressure of CO and H2 and neutral conditions using DPPB provided the 2(5//)-furanone 69. It was claimed that H2 was required for this reaction [16]. 

Tanaka et al. developed a Rh-catalyzed asymmetric one-pot transesterification and [2+2+2] cyclotrimerization using nonracemic ligand 415 in the synthesis of enantio-enriched 3,3-disubstituted phthalides (R R ) (Scheme 2-39)P The chiral Rh complex with 415 efficiently desymmetrized dipropargyl alcohols 413 (R = R -OC-) in the reaction with 412 to give phthalides 414 (R = R -C=C-) in up to 87% yield and 93% ee. Also, the kinetic resolution of racemic tertiary propargylic alcohols... 

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