Propargylic alcohol, double addition

We now report the synthesis of new antibacterial 3H-pyrazoles by regioselective 1,3-dipolar cycloaddition of the versatile 2-diazopropane to nonprotected disubstituted propargyl alcohols and that the unsubstituted propar-gyl alcohol allows the double addition of 2-diazopropane and gives a 3H-pyrazole with formal insertion of the dimethylcarbene into a carbon-carbon bond. We also show that the photolysis of the 3H-pyrazoles leads to new alcohols containing the cyclopropenyl unit. 

Addition of acetylene 9 to aldehyde 12 afforded 85% of propargylic alcohol 13 as a mixture of diastereomers. Hydrogenation reduced the triple bond and both double bonds and cleaved the Cbz groups providing 94%... 

The double phosphinylation of propargylic alcohols with diphenylphos-phine oxide to form 2,3-bis(diphenylphosphinyl)-1-propenes is catalyzed by a thiolate-bridged diruthenium complex (Scheme 28) [69]. It has been shown that the reaction proceeds via three ruthenium-catalyzed transformations propargylation of the phosphine oxide, alkyne to allene isomerization, and addition of phosphine oxide to the allene structure. 

Thus, the optimized carbometallation reaction of propargylic alcohols with aromatic Grignard reagents proceeds without an additional metal catalyst and leads to the formation of an alkenyl fluoride. The stereoselective defluorometallation proceeds to form predominantly the fluorinated (Z)-carbon-carbon double bond in the final allene 276. Two reasons were proposed by the authors for such a high level of stereoselectivity the defluorometallation is favored from the intermediate... 

Another example of the acid-catalysed intramolecular cyclization of diazoketones cf. refs. 58, 92, 93) is a high-yielding preparation of polycyclic enones (101) from diazoketones (100). Further reports have appeared on the preparation of fused cyclopentanones by condensations between acetonedicar-boxylate and a-diketones yields are higher if the substituents on the latter substrates are small. An alternative approach to polycyclopentanoids, consisting of successive additions of propargyl alcohol anions to cyclopentanones followed by double dehydrative cyclization and hydrogenation, has been used to prepare the potential dodecahedrane precursor (102) cf ref. 63). The cage compound (103), obtained from 1,4-naphthoquinones and cyclopentadiene, produces the polycyclopentanoid (104) under acyloin condensation conditions. ... 

In the steroid series, o-ring enlargement accompanies reaction of a secondary alcohol with PBrs (eq 7.) It should be noted that reaction of Phosphorus(V) Chloride with this same substrate gave direct replacement of the OH with Cl with inversion of configuration. Rearrangement and addition of bromine across a double bond has been noted in the reaction with a propargyl alcohol derivative (eq 3). ... 

The second starting material, mesylate 426, was synthesized from alcohol 422. Swern oxidation followed by addition of propargyl zinc bromide led to compound 423 in 79% yield, which was converted into thionocarbonate 424 (41% yield over three steps). Radical ring closure with tributyltin hydride and oxidation with Dess-Martin periodinane afforded ketone 425. Treatment with DMAP led to the rearrangement of the double bond and subsequent reduction with sodium borohydride and mesylation gave compotmd 426 (Scheme 8.6). 

The addition reaction goes much more smoothly with acetylenes than with olefins. For example, tri- -propyltin hydride reacts smoothly with propargyl alephol in the absence of a catalyst, but not with allyl alcohol. Results are summarized in Table IV. Since the adduct still contains a double bond, further addition leading to the formation of a product containing two tin atoms is possible, and has been shown to occur with acetylene and phenylacetylene. Since olefins are less reactive, the reaction can be interrupted after the first step. 

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