Enantioselective addition of 2-methyl-3-butyn-2-ol to aldehydes: preparation of 3-hydroxy-1-butynes

We report the first example of enantioselective aldehyde additions of 2-methyl-3-butyn-2-ol, a commodity bulk chemical that is readily available. Following a facile fragmentation reaction, the addition reactions provide access to optically active terminal acetylenes as useful building blocks for asymmetric synthesis.     

Synthesis of 1-Bromo-3-butyn-2-one and 1,3-Dibromo-3-buten-2-one

Synthetic procedures for the preparation of 1-bromo-3-butyn-2-one and 1,3-dibromo-3-buten-2-one are given. These compounds are prepared from 2-bromomethyl-2-vinyl-1,3-dioxolane, which can readily be prepared from 2-ethyl- 2-methyl-1,3-dioxolane. The synthetic routes are as follows: 2-bromomethyl-2-vinyl-1,3-dioxolane is converted to 2-(1,2-dibromoethyl)-2-bromomethyl-1,3-dioxolane. Double dehydrobromination with ^tBuOK affords 2-ethynyl-2-bromomethyl-1,3-dioxolane. Formolysis with formic acid gives 1-bromo-3-butyn-2-one. Deacetalized 2-bromoethyl-2-vinyl-1,3-dioxolane was treated with Br₂ and Li₂CO₃/12-crown-4 in tetrahydrofuran to give 1,3-dibrom-3-buten-2-one in moderate yield.     

Lipase-catalyzed kinetic resolution of 3-butyn-2-ol

Optically active 3-butyn-2-ol, an important building block, was synthesized successfully using lipase-catalyzed kinetic resolution. Starting from the thus obtained 3-butyn-2-ol, several 4-aryl-substituted compounds were synthesized enantioselectively.     

Calorimetric and computational study of 3-buten-1-ol and 3-butyn-1-ol. Estimation of the enthalpies of formation of 1-alkenols and 1-alkynols

The enthalpies of combustion and vaporization of 3-buten-1-ol and 3-butyn-1-ol have been measured by static bomb combustion calorimetry and correlation gas chromatography techniques, respectively, and the gas-phase enthalpies of formation, Delta(f)H degrees (m)(g), have been determined, the values being -147.3 +/- 1.8 and 16.7 +/- 1.6 kJ mol(-1), for 3-buten-1-ol and 3-butyn-1-ol, respectively. High level calculations at the G2 and G3 levels have also been carried out. Relationships between the enthalpies of formation of 1-alkanols, 1-alkenols and 1-alkynols and with the corresponding hydrocarbons have been discussed. From the calculated contributions to Delta(f)H degrees (m)(g) for the substitutions of CH(3) by CH(2)OH, CH(3)CH(2) by CH(2)=CH and CH(3)CH(2) by CH triple bond C, we have estimated the Delta(f)H degrees (m)(g) values for 3-buten-1-ol and 3-butyn-1-ol, in excellent agreement with the experimental ones. Delta(f)H degrees (m)(g) values for 1-alkenols and 1-alkynols up to 10 carbon atoms have also been estimated.     

One-pot synthesis of 1-monosubstituted-1, 2, 3-triazoles from 2-methyl-3-butyn-2-ol

An efficient method for the synthesis of 1-monosubstituted-1, 2, 3-triazoles from 2-methyl-3-butyn-2-ol under copper catalyst conditions has been developed through a one-step one-pot sequence. This method provides a concise and efficient pathway to synthesize 1-monosubstituted-1, 2, 3-triazole derivatives in good to excellent yields.     

Michael addition of 3-bromoinden-1-one: an expedient synthesis of 5-bromo-3-trifluoroacetamidoindan-1-one

The Michael addition of 5-bromo-inden-1-one with ammonia followed by acylation with trifluoroacetic anhydride provides 5-bromo-3-trifluoroacetamidoindan-1-one in 51% yield in one-pot.     

Tertiary Acetylenic Alcohols and Diols on the Basis of Phenylacetylene and 2-Methyl-3-butyn-2-ol

A procedure has been proposed for the synthesis of tertiary acetylenic alcohols and diols by treatment of phenylacetylene or 2-methyl-3-butyn-2-ol with butyllithium and subsequent reaction of lithium phenylacetylide or lithium 4-lithio-2-methyl-3-butyn-2-olate thus obtained with alicyclic, aromatic, and terpene ketones.     

Cu(I)-catalyzed cascade reaction of N-tosylhydrazones with 3-butyn-1-ol: A new synthesis of tetrahydrofurans

The Cu(I)-catalyzed cascade coupling/cyclization reaction of N-tosylhydrazones with 3-butyn-1-ol has been explored. This new strategy represents a simple platform for the synthesis of tetrahydrofurans in moderate to good yields.     

Reaction of Grignard Compounds with 4-Chloro-2-methyl-3-butyn-2-ol in Diethyl Ether Equivalents

Reactions of RMgX·THF complexes with 4-chloro-2-methyl-3-butyn-2-ol in aromatic hydrocarbons were studied. The complexes formed by arylmagnesium halides require the presence of anisole for the reaction to occur. 4-Chloro-2-methyl-3-butyn-2-ol can be synthesized by reaction of 2-methyl-3-butyn-2-ol with sodium hypochloride in the two-phase system water-benzene.     

Unexpected selective monoadduct formation from 2-methyl-3-butyn-2-ol and α,ω-diiodoperfluorobutane

Radical chain addition of α,ω-diiodoperfluorobutane to 2-methyl-3-buten-2-ol and 2-methyl-3-butyn-2-ol has been studied. The Huang sulfinatodehalogenation system, used as initiator, gave satisfactory conversion yields of the starting diiodide when compared to more classical initiators (AIBN, Fe, triethylborane). Addition to the alkenol yields classically the bis-adduct with variable amounts of the monoadduct. On the contrary the alkynol leads exclusively to the monoadduct formation, in high yield. Some considerations are proposed for interpreting this result. The monoadduct selectively obtained constitutes a powerful intermediate for synthesis.