Guerbet reaction of primary alcohols leading to beta-alkylated dimer alcohols catalyzed by iridium complexes

[IrCl(cod)]2 and [Cp*IrCl2]2 complexes catalyzed efficiently the Guerbet reaction of primary alcohols to beta-alkylated dimer alcohols in good yields. For instance, the reaction of 1-butanol in the presence of [Cp*IrCl2]2 (1 mol %), t-BuOK (40 mol %), and 1,7-octadiene (10 mol %) produced 2-ethyl-1-hexanol in 93% yield. Various primary alcohols undergo the Guerbet reaction under the influence of Ir complexes to give the corresponding dimer alcohols in good yields. This method provides an alternative direct route to beta-alkylated primary alcohols which are prepared by aldol condensation of aldehydes followed by hydrogenation.     

Direct beta-alkylation of secondary alcohols with primary alcohols catalyzed by a CpIr complex

A new catalytic system for beta-alkylation of secondary alcohols has been developed. In the presence of [CpIrCl(2)](2) (Cp = pentamethylcyclopentadienyl) catalyst and base, the reactions of various secondary alcohols with primary alcohols give beta-alkylated higher alcohols in good to excellent yields without any hydrogen acceptor or hydrogen donor. This reaction proceeds via successive hydrogen-transfer reactions and aldol condensation. [reaction: see text]     

Intermolecular [4 + 2] cycloaddition of o-quinodimethanes derived from ene-bis(sulfinylallenes)

Intermolecular [4 + 2] cycloaddition of o-quinodimethanes, prepared in situ from ene-bis(propargyl alcohols) and benzenesulfenyl chloride via ene-bis(sulfinylallene) formation, was investigated. Benzene-bridged bis(propargyl alcohols) reacted with both electron-deficient and electron-rich olefins to give the corresponding [4 + 2] cycloadducts. Ethylene-bridged bis(propargyl alcohols) underwent similar cycloaddition with electron-deficient olefins. Construction of some heterocycles based on the newly developed sequential reaction is also described.     

An efficient route to alkyl chlorides from alcohols using the complex TCT/DMF

[reaction: see text] Efficient conversion of alcohols and beta-amino alcohols to the corresponding chlorides (and bromides) can be carried out at room temperature in methylene chloride, using 2,4,6-trichloro[1,3,5]triazine and N,N-dimethyl formamide. This procedure can also be applied to optically active carbinols.     

Asymmetric aminolysis of aromatic epoxides: a facile catalytic enantioselective synthesis of anti-beta-amino alcohols

[reaction: see text] The first asymmetric aminolysis of trans-aromatic epoxides with anilines is described. The process affords enantioenriched anti-beta-amino alcohols in up to 99% ee. The complete regio- and diastereoselectivity observed uses commercially available [Cr(Salen)Cl] as a Lewis acid catalyst and in combination with a very simple experimental procedure renders the present reaction a facile and practical tool for the synthesis of chiral nonracemic anti-beta-amino alcohols.     

Sequential pericyclic reaction of ene-diallenes: an efficient approach to the steroid skeleton

[reaction: see text] The one-pot construction of polycyclic aromatic systems from acyclic ene-bis(propargyl alcohols) was achieved through a tandem dual [2,3]-sigmatropic rearrangement/6pi-electrocyclic reaction/intramolecular [4 + 2] cycloaddition sequence. A steroidal compound was conveniently synthesized using the present method.     

Rhodium(I)-catalyzed carbonyl allenylation versus propargylation via redox transmetalation across tetragonal tin(II) oxide

[reaction: see text] A reagent combination of beta-SnO and catalytic [Rh(COD)Cl](2) in THF-H(2)O promotes the reaction of propargyl bromides and aldehydes and directs the regioselectivity toward the formation of either allenic alcohols or homopropargylic alcohols. This highly regioselective either/or transformation proceeds via a transmetalation from rhodium to tin, in which metallotropic rearrangement between a propargylmetal and allenylmetal is arrested.     

Synthesis and transformation of [difluoro(phenylseleno)methyl]- trimethylsilane

[reaction: see text] A novel and efficient strategy was developed to synthesize [difluoro(phenylseleno)methyl]trimethylsilane (PhSeCF(2)TMS, 2), which was further utilized as a nucleophilic difluoromethylating reagent to incorporate the difluoro(phenylseleno)methyl (PhSeCF(2)) group into carbonyl compounds in good yields. The resulting PhSeCF(2)-containing alcohols 3 could be conveniently converted into corresponding difluoromethyl alcohols 4 by a radical deselenylation.     

High stereoselective preparation of O-protected 2-trifluoromethyl 3-bromoallylic alcohols from 1,1-dibromo-1-alkenes

A highly stereoselective lithium-bromine exchange reaction of 2-trifluoromethyl-3,3-dibromoallylic alcohols is described. (E)- and (Z)-2-trifluoro-3-bromoallylic alcohols were obtained in THF and hexane, respectively. The lithium carbenoid intermediate was stable even at -40 degrees C and could be trapped by various electrophiles to afford functionalized 2-trifluoromethyl-3-bromoallylic alcohols. [reaction: see text]     

C−C Bond Formation between Fischer Carbene Complexes and Allylic Alcohols by a [3,4] Sigmatropic Rearrangement Promoted by a [1,2] M(CO)5 Shift

A [1,2] M(CO) ₅ shift promotes a [3,4] sigmatropic rearrangement after the addition of allylic alcohols to Fischer alkenylcarbene complexes of tungsten or chromium in the presence of alkoxide ions. This opens a new synthetic route to the adducts 1 . The reaction is also applicable to propargylic alcohols. [M]=Mo(CO)₅, W(CO)₅.     

A facile and efficient [bmim]N3 catalyzed direct oxidative esterification of arylaldehydes with alcohols

Task-specific ionic liquid, [bmim]N₃ was used as an effective catalyst and reaction medium for the direct oxidative esterification of arylaldehydes with alcohols. The oxidative esterification reaction of a variety of arylaldehydes took place smoothly with some primary and secondary alcohols in [bmim]N₃. Satisfactory results were obtained with arylaldehydes containing electron withdrawing groups. Tertiary alcohols did not react under these conditions.     

Tf2NH-catalyzed,highly regio-and stereo-selective synthesis of trisubstituted alkenes and indane derivatives from benzylic alcohols and alkenes

A reaction of benzylic alcohols with alkenes has been developed in the presence of bis(trifluoromethane)sulfonimide for the synthesis of trisubstituted alkenes and indane derivatives with high stereoselectivity.In general,benzylic alcohols react with 1,1-diaryl alkenes to afford trisubstituted alkenes,and the reaction with 1,2-disubstituted and trisubstituted alkenes affords indane derivatives through a [3 + 2] annulation reaction.     

Tandem Prins/Friedel–Crafts cyclization for stereoselective synthesis of heterotricyclic systems

Homoallylic substrates such as (E)-6-arylhex-3-enyl alcohols, N-tosylamides, and thiols undergo smooth cross-coupling with various aldehydes in the presence of 10 mol % Sc(OTf)(3) and 30 mol % TsOH to afford the trans-fused hexahydro-1H-benzo[f]isochromenes, N-tosyloctahydrobenzo[f]isoquinolines, and hexahydro-1H-benzo[f]isothiochromenes, respectively. However, the cross-coupling of (Z)-olefins such as 6-arylhex-3-enyl alcohols, N-tosylamides, and thiols with aldehydes affords the corresponding hexahydro-1H-benzo[f]isochromenes, N-tosyloctahydrobenzo[f]isoquinolines, and hexahydro-1H-benzo[f]isothiochromenes with complete cis selectivity via intramolecular Prins-, aza-Prins-, and thia-Prins/Friedel-Crafts cyclizations, respectively. Though the Prins cyclization proceeds smoothly under the influence of Sc(OTf)(3), high conversions and enhanced reaction rates are achieved using a mixture of Sc(OTf)(3) and TsOH (1:3).     

Highly efficient chemical kinetic resolution of bishomoallylic alcohols: synthesis of (R)-sulcatol

[reaction: see text] A highly efficient chemical kinetic resolution of bishomoallylic alcohols was developed when the alcohols underwent In(OTf)(3)-catalyzed 3,5-oxonium-ene-type cyclization with steroidal aldehyde 2. Consistently high enantiomeric excess (up to >99%) was obtained.     

DABCO catalyzed reaction of various nucleophiles with activated alkynes leading to the formation of alkenoic acid esters, 1,4-dioxane, morpholine, and piperazinone derivatives

The reaction of acids, alcohols, acylamides, 1,2-diols, 1,2-diamines or amino alcohols with activated alkynes catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) was systematically investigated. A series of unsaturated alkenoic acid esters or heterocycles were formed in the reaction of monobasic or dibasic nucleophiles in excellent yields, respectively.     

Synthesis of new planar chiral [2.2]paracyclophane Schiff base ligands and their application in the asymmetric Henry reaction

A series of new planar and central chiral ligands based on [2.2]paracyclophane backbones were designed and prepared from enantiomerically pure 4-amino-13-bromo[2.2]paracyclophane and commercially available chiral amino alcohols. Their application in a copper-catalyzed asymmetric Henry reaction resulted in secondary alcohols with high yield and excellent selectivity for active aldehydes (up to 94% ee). This is a successful example of employing planar chiral [2.2]paracyclophane ligands in copper-catalyzed reaction.     

Gallium-mediated allyl transfer from bulky homoallylic alcohol to aldehydes via retro-allylation: stereoselective synthesis of both erythro- and threo-homoallylic alcohols

Retro-allylation of bulky gallium homoallylic alkoxides occurs to generate (Z)- and (E)-crotylgallium reagents stereospecifically, starting from erythro- and threo-homoallylic alcohols, respectively. The (Z)- and (E)-crotylgallium reagents immediately reacted with aromatic aldehydes to afford the corresponding erythro- and threo-homoallylic alcohols, respectively. [reaction: see text]     

[Sn(TPP)(BF4)2]: An efficient and reusable catalyst for chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane

Tin(IV)tetraphenylporphyrinato tetrafluoroborate, [Sn^IV(TPP)(BF₄)₂], was used as an efficient catalyst for trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS). High-valent [Sn^IV(TPP)(BF₄)₂] catalyzes trimethylsilylation of primary, secondary and tertiary alcohols as well as phenols, and the corresponding TMS-ethers were obtained in high yields and short reaction times at room temperature. While, under the same reaction conditions [Sn^IV(TPP)Cl₂] is less efficient to catalyze these reactions. One important feature of this catalyst is its ability in the chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity.     

On possible redirection of the course of anionic oxy-cope rearrangements

The β, γ-unsaturated ketones bicyclo[2.2.1]hept-2-en-7-one (10) and 7,7-dimethoxybicyclo[2.2.1]hept-2-en-5-one (15) have been condensed with 1-metalated trans-1-methoxybutadienes (7a or 7b) and 2-isopropenylcyclopentenes (8b or 8c). Oxyanion formation within the resulting alcohols is followed by skeletal rearrangement at room temperature. Careful product analysis has revealed the [3,3] sigmatropic reaction manifold to be followed almost exclusively. Only in the case of 13 is a modest amount (4%) of formal antarafacialretention [1,3] sigmatropic bridgehead carbon migration in evidence. Consequently, the structural features inherent to these alcohols are not conducive to redirecting electronic reorganization to an alternative isomerization process.     

Reactions of 4,7-dibromo[1,2,5]thiadiazolo[3,4-d]pyridazine with alcohols

Russian Chemical Bulletin - The reaction of 4,7-dibromo[1,2,5]thiadiazolo[3,4-d]pyridazine with alcohols and sodium alkoxides was evaluated under various conditions. Depending on the reaction...