Allenic Alcohols Research Articles

Synthesis of fluorinated allenes via palladium-catalyzed monofluoromethylation using FBSM

Palladium-catalyzed monofluoromethylation of substituted 2-bromo-1,3-dienes using fluorobis(phenylsulfonyl)methane (FBSM) as a pronucleophile gave previously unknown monofluoromethylated allenes in high yields, which are the isosteres of biologically attractive allenic alcohols.

In-Mediated Synthesis of Allenic Esters and their Cyclization to 2-Naphthoates

Functionalized α-hydroxyallenic esters combine two useful functions: an allenic alcohol and an allenic ester, and therefore are useful intermediates in synthetic chemistry, as well as structural units of many natural compounds. Herein, a simple and general method for their synthesis, based on the formation of organoindium intermediates, is described. These compounds were shown to undergo an interesting Au+-catalyzed cyclization to 2-naphthoate derivatives.

Rationalizing the Formation of Damascenone: Synthesis and Hydrolysis of Damascenone Precursors and Their Analogues, in both Aglycone and Glycoconjugate Forms

Storage of megastigma-4,6,7-trien-3,9-diol (5), and megastigma-3,4-dien-7-yn-9-ol (6) in aqueous ethanol solution at pH 3.0 and 3.2 gave exclusively damascenone (1) and damascenone adducts at room temperature. The diol (5) had half-lives for the conversion of 32 and 48 h at pH 3.0 and pH 3.2, respectively. The acetylenic alcohol (6) had half-lives of 40 and 65 h at the same pH levels. In order to study the reactivity of the C-9 hydroxyl function in 5 and in the previously investigated allenic triol 2, two model compounds, megastigma-4,6,7-trien-9-ol (7) and megastigma-6,7-dien-9-ol (8) were synthesized. No 1,3-transposition of oxygen to form analogues of damascenone was observed when 7 and 8 were subjected to mild acidic conditions. Such transposition takes place only with highly conjugated acetylenic precursors such as 6 or tertiary allenic alcohols such as 2. The placement of glucose at C-3 of 5 and at C-9 of 6 gave the glycosides 9 and 10, respectively. The effect of such glucoconjugation was to increase the observed half-lives by a factor of only 1.6-1.7 for the allenic glucoside 9, and by 2.1-2.2 for the acetylenic glucoside 10. These studies indicate that the effect of glycosylation on damascenone formation is probably not important on the time scale of wine making and maturation.

A Simple Approach To Separate a Mixture of Homopropargylic and Allenic Alcohols

A simple and practical approach to separate homopropargylic alcohol from allenic alcohol has been developed. It involves the formation of an insoluble silver acetylide species between silver nitrate and homopropargylic alcohol in aqueous acetone which can be separated from the allenic alcohol through a simple filtration. The homopropargylic alcohol can subsequently be recovered by hydrolysis with 1 N HCl. This protocol has been applied to the separation of a mixture of chiral homopropargylic and allenic alcohols in excellent yields with retention of absolute stereochemistry.

ChemInform Abstract: Regio‐ and Stereoselective Direct Cross‐Coupling of Aromatic Imines with Allenic Alcohols.

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Reprint of “Allene–alkyne cross-coupling for stereoselective synthesis of substituted 1,4-dienes and cross-conjugated trienes”

Titanium-mediated cross-coupling of allenic alcohols with alkynes has been investigated. Divergent reaction pathways were discovered that provide either stereodefined 1,4-dienes or substituted cross-conjugated trienes. In short, allene substitution plays a critical role in the determination of reaction pathway.

Regio- and Stereoselective Direct Cross-Coupling of Aromatic Imines with Allenic Alcohols.

We describe a titanium-mediated reaction for the convergent coupling of allenic alcohols with aromatic imines. Overall, the bond formation occurs at the central carbon of the allene, proceeds with net allylic transposition, and provides substituted 1,3-dienes bearing allylic amine functionality in a regio- and stereoselective fashion.

Allene–alkyne cross-coupling for stereoselective synthesis of substituted 1,4-dienes and cross-conjugated trienes

Titanium-mediated cross-coupling of allenic alcohols with alkynes has been investigated. Divergent reaction pathways were discovered that provide either stereodefined 1,4-dienes or substituted cross-conjugated trienes. In short, allene substitution plays a critical role in the determination of reaction pathway.

Studies into Asymmetric Catalysis of the Nozaki–Hiyama Allenylation

From aldehydes to allenic alcohols: Studies into the asymmetric catalysis of the Nozaki–Hiyama allenylation are described. Ligand 1 a is effective for the enantioselective allenylations of various aldehydes, with the generation of products with ee values ranging from 72–83 %. The products can be easily desilylated or used as allenylsilanes. DIPEA=diisopropylethylamine, DMI=1,3-dimethyl-2-imidazolidinone, DMS=dimethylsilyl, TMS=trimethylsilyl. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z502871_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Internal Nucleophilic Termination in Acid‐Mediated Polyene Cyclizations Part 4

AbstractTreatment of the unsaturated bicyclic homoallylic alcohols (E)‐ and (Z)‐5 and (Z)‐ and (E)‐10 and allenic alcohol 16 with an excess of ClSO3H in 2‐nitropropane or CH2Cl2 at − 80° afforded, in moderate yields (ca. 30–70%), diastereoisomer mixtures of racemic tetracyclic ethers 12a–c (Table 1) and 17a,b (Table 2), respectively. These kinetically controlled stereospecific transformations are believed to proceed via concerted or nonconcerted pathways (see Schemes 4 and 6) and the results are fully consistent with our earlier work. Representing novel didehydro bridged analogues of known, olfactively active labdane tricyclic ethers, the organoleptic properties of 12a–c and 17a,b are briefly described, especially those of 12c which, in the context of structure–activity studies, is a racemic didehydro analogue of the known ambergris odorant Ambrox®.

Silicon‐Assisted Propargylic Transfer to Aldehydes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Studies toward the Synthesis of Furanocembrane Bipinnatin J: Synthesis of a 2,3,5-Trisubstituted Furfuryl Ether Intermediate

Synthesis of 2,3,5-trisubstituted furfuryl ether (29), a potential intermediate in a synthetic approach to bipinnatin J, was achieved by a combination ofetherification and Stille cross-coupling reaction. Unexpectedly, an intramolecular coupling reaction of 29 proceeded through S N 2' substitution to give 15-membered furfuryl ether (30). Formation of γ-butenolide (34) was also accomplished by a ruthenium-catalyzed carbonylation of allenic alcohol (33).

Rhodium(I)‐Catalyzed Carbonyl Allenylation versus Propargylation via Redox Transmetalation Across Tetragonal Tin(II) Oxide.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Palladium‐Catalyzed Coupling Reaction of Allenic Alcohols with Aryl‐ and Alkenylboronic Acids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Internal Nucleophilic Termination in Acid‐Mediated Polyene Cyclizations. Part 3

AbstractTreatment of the unsaturated allenic alcohols (E)‐7, (Z)‐7, 10, 13, and 19 with an excess of FSO3H in 2‐nitropropane at −90° to −30° afforded, in 68–85% yield, diastereoisomer mixtures of racemic tricyclic ethers 14a–d and 20a–d, respectively (Schemes 3 and 5), with high stereoselectivity (see Table and Scheme 6). These stereospecific transformations represent the first reported examples of an acid‐mediated polyene cyclization, in which an alkene is the initiating group and an allenic alcohol serves as the internal terminator. In close analogy to our earlier work, a nonsynchronous process is postulated, whereby the stereochemical course of cyclization is directed by the conformational structure of an intermediate cyclohexyl cation (see Schemes 3 and 6). In addition, the organoleptic properties of 14c and 20c, racemic didehydro and methyl didehydro analogues, respectively, of the known odorant Ambrox® ((−)‐4f), are briefly discussed.

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.

Indium‐Mediated Reaction of Trialkylsilyl Propargyl Bromide with Aldehydes: Highly Regioselective Synthesis of Allenic and Homopropargylic Alcohols.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Palladium-catalysed coupling reaction of allenic alcohols with aryl- and alkenylboronic acids.

The direct coupling of aryl- and alkenylboronic acids with allenic alcohols has been achieved using a palladium catalyst to yield various substituted dienes and trienes in high yields.

Silicon-assisted propargylic transfer to aldehydes

A new and efficient method of obtaining homopropargylic alcohols via homopropargylic transfer from the allenic alcohol to various aldehydes in the presence of Lewis acid catalysts is described; stereochemical studies have shown that this process is the first oxonium [3,3]-sigmatropic rearrangement of an allenic alcohol to a homopropargylic alcohol in the presence of aldehydes and Lewis acid.

Regio‐ and Stereocontrolled Dimerization of Allenic Alcohols via Introduction of an Acetoxy Group Using Ruthenium Catalysis.

AbstractFor Abstract see ChemInform Abstract in Full Text.