Allenes allyl alcohols

As with i -substituted allyl alcohols, 2,i -substituted allyl alcohols are epoxidized in excellent enantioselectivity. Examples of AE reactions of this class of substrate are shown below. Epoxide 23 was utilized to prepare chiral allene oxides, which were ring opened with TBAF to provide chiral a-fluoroketones. Epoxide 24 was used to prepare 5,8-disubstituted indolizidines and epoxide 25 was utilized in the formal synthesis of macrosphelide A. Epoxide 26 represents an AE reaction on the very electron deficient 2-cyanoallylic alcohols and epoxide 27 was an intermediate in the total synthesis of (+)-varantmycin. 

The base-catalyzed addition of allyl alcohol to (phenylsulfonyl)allene (112) gives the adduct which rearranges to ff-keto sulfone (113) on the treatment with KH in HMPA (equation 88)72. 

Allene, l,3-di-ferf-butyl-l,3-dicyano- [2,3-Pentadienedimtnle, 2,4-bis(l,l-di-methylethyl) ], 55, 38 ALLYL ALCOHOL [2 Propen 1 ol], 55, 1 Amberhte IRA-400, 55, 5 Amine, diethyl- [Ethanamme, IV-ethyl-],... 

Allenic alcohols couple with allyl indium reagents at 140°C to give allylic alcohol products. Similarly, (o-hydroxy lactones couple with organoindium reagents. 

Burger2 has shown that alkynes undergo both Lewis acid-catalyzed and thermal carbonyl-yne reactions with 3,3,3-trifluoropyruvates to give allenes. Reaction of 1 (Equation (2)) occurs to give a 1 1 mixture of diastereomeric allenyl carbinols 2. Alternatively, reaction of hexyne 1 and methyl trifluoropyruvate with MgBr2-OEt2 at low temperature afforded 2 as an 8 1 mixture of diastereomers. The thermal reaction does not suffer from allylic alcohol byproducts arising from reaction of the substrate with the Lewis acid.3... 

Allylphosphonium salts are synthesized by substitution of allyl halides with PPh3. The use of allyl alcohol, allyl acetate, or nitropropene with a palladium catalyst has also been reported.19 It is shown in this study that the organophosphorous compounds can be obtained by a palladium-catalyzed addition to an allene. A notable aspect of this method is that it can control the stereochemistry of the phosphonium salt, and that (Z)-allylphosphonium salts have been obtained in pure form for the first time. 

Thermodynamic and kinetic data for Cope rearrangements leading to allenes have been measured [511]. For preparatively useful yields the equilibrium can be shifted to the allene, for example by the classical use of allylic alcohols leading to carbonyl compounds [512],... 

One of the rare applications of selenium-substituted allenes was recently reported by Ma et al. [182]. The allenyl selenide 352 undergoes an iodohydroxylation or iodo-amination, depending on the amount of water used, leading to the formation of allyl alcohol 353 and allylacetamide 354 (Scheme 8.97). When the reaction is performed with 12-16 equiv. of water, allyl alcohol 353 is exclusively formed, whereas the use of 1 equiv. of water exclusively provides the amide 354 in 64% yield. 

The reaction of HOC1 with allenes also yielded a mixture of regioisomeric allylic alcohols with the chlorine atom connected to the central carbon atom and the OH connected to the more substituted carbon atom [15]. 

The intermediate product 162, formed from the nudeophilic addition of 1,2-alle-nic phosphonate or 1,2-allenic phosphine oxide with allylic alcohol, would also undergo a Claisen rearrangement to form 2-oxo-5-alkenyl phosphonate or phosphine oxide 163 [85], The rearrangement is accelerated by the carbanionic nature of the intermediate 162. For the conjugate addition step, the reaction temperature is crucial since the reaction at 0 °C afforded mainly /i,y-unsaturated product whereas a,/8-unsaturated products were formed at 20 °C. 

The iodohydroxylation of 1,2-allenyl sulfoxide 171 with I2 in the presence of H20 exhibits E-selectivity leading to (E)-2-iodo-3-hydroxy-l-alkenyl sulfoxide [88]. By using Br2, CuBr2 or NBS, (E)-2-bromo-3-hydroxy-l-alkenyl sulfoxide is produced. For the chlorohydroxylation of a sulfoxide, CuCl2 and silica gel were used to mix with the sulfoxide to deliver the (E)-chlorohydroxylation products highly stereoselec-tively [88]. The chirality in the allene moiety can be efficiently transferred to the final allylic alcohols. Under the catalysis of a Pd or Ni complex, the C-X and C-S bonds can be coupled to introduce different substituent(s) into the different locations of the C=C bond. 

Similarly, allenes [32] and alkynols [33] were used as starting materials and their carbonylation provides /3,y-unsaturated acids and unsaturated diacids, respectively. The specific reactivity of alkynols is explained by three formal steps during nickel catalysis (i) carbonylation of the triple bond leading to an acid containing an allylic alcohol moiety (ii) second carbonylation of the double bond to provide a hydroxydiacid and (iii) a dehydration step giving the corresponding unsaturated diacid (Scheme 2). 

Similarly, the oxidation of iodocyclohexane by DMD under a nitrogen-gas atmosphere leads to the iodohydrin and diol as unexpected products (equation 24). The iodohydrin, formed as the major product, clearly reveals that hypoiodous acid (HOI) is generated in situ, which adds to the liberated cyclohexene. Indeed, when methyl iodide (Mel) is oxidized by DMD at subambient temperature in the presence of cyclohexene, the corresponding iodohydrin is obtained in very good yield The latter method may be utilized for the preparation of allylic alcohols with a vinylic iodo functional group from allenes (equation 25) . ... 

Steiically congested cw-aziridines such as 137 were prepared from the deiivatized amino allyl alcohol precursor 136 through a palladium-catalyzed cyclization reaction <99TL1331>. This methodology has also been extended to the cyclization of amino allenes <99JOC2992>. 

One of the first optically active allenes reported was synthesized by enantioselective dehydration of a racemic allylic alcohol in the presence of (+)-10-camphorsulfonic acid as the chiral catalyst125,126. The initial optical rotation of the tetraarylallene is low, but can be increased to [a],2/1 +351 (cyclohexane) after several recrystallizations. 

Type I (fast homodimerization) Terminal olefins, allylsilanes" Terminal olefins, allylsilanes," 1° allylic alcohols, ethers, and esters, " allyl boronate esters, allyl halides, alkyl-substituted allenes Terminal olefms, allyl boronate esters, 1° allylic alcohols, ethers, and esters,styrenes (no large ortho substit.), " " allyl allylsilanes, allyl sulfides, allyl phosphonates, " allyl phosphine oxides, protected allylamines ... 

Dehydration of alcohols, diols, or glycols does not give allenes in appreciable yield because conjugated dienes [30] are the main product. Even allyl alcohol cannot be suitably dehydrated to allene in reasonable yields. When elimination to the conjugated diene is prevented, as for 2,2-dimethyl-4-hexene-3-ol, the allene is still obtained in only 19% yield [31]. 

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... 

Predictably, with enynes dihalocarbene addition occurs preferentially with the double bond (equation 17).63 64 The reaction of dichlorocarbene with allenes usually gives rise to spiro-linked dichlorocyclopro-panes (equation 18),65 but rearranged products are obtained in some cases (equation 19).65 66 Somewhat surprisingly, a measure of stereoselectivity has been observed in the formation of dichlorocyclopro-pylcarbinols from secondary allylic alcohols and dichlorocarbene (equation 20).67... 

N-Tosyl carbamates, such as 325, derived from allylic alcohols, undergo the Pd(II)-catalysed cyclization to furnish oxazolidinones 326 under 1 atm of CO439. Analogous Pd(II)-catalysed N-cyclization of allenic N-tosylcarbamates has generated the corresponding vinylpalladium intermediate that could be further alkylated440. 

More recently, this kinetic resolution has been applied successfully to some primary allylic alcohols and an allenic alcohol.7... 

A three-component reaction based on the umpolung of re-allylpalladium (II) complexes indium metal was reported by Grigg and co-workers (Scheme 8.31) [74]. In this reaction, the electrophilic nature of the n-allyl palladium species generated from aryl halides and allenes is reversed by transmetallation with indium metal. The resultant nucleophilic allylindium reagent subsequently adds to the third component - aldehyde [75] or imine [76] - to give the corresponding homo-allylic alcohol 64 or amine 65 respectively. 

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