149713-24-6

In this Letter, a catalytic diastereoselective hetero-Diels-Alder reaction of α-haloacroleins with less polarized alkenes was developed, and the resulting 3,4-dihydropyrans were produced in high yields with a broad substate scope. Mechanism studies showed that 3,4-dihydropyran was produced from the ring expansion of cyclobutane, which was generated in the ring contraction of the initially formed unstable 3,4-dihydropyran conformer.

We report a nickel/NHC-catalyzed branched-selective α-crotylation of simple ketones using 1,3-butadiene as the alkylation agent. This reaction is regioselective and operated under pH and redox-neutral conditions. Water was used as the sole additive, which significantly accelerates the transformation.

The invention discloses a gamma-alkenyl ketone preparation method, wherein the target product can be obtained at high yield and high regioselectivity by using acetophenone and 1,3-butadiene as raw materials in the presence of an organic solvent, a catalyst, an additive and a ligand. According to the invention, the method has advantages of high atom economy, high regioselectivity, high yield and the like, can achieve the efficient conversion from a cheap basic organic chemical product 1,3-butadiene to high-added-value gamma-alkenyl ketone, and uses the cheap catalyst, so that the reaction conditions are neutral and mild, and the experimental operation is safe and simple; and the synthesized gamma-alkenyl ketone is a useful synthetic intermediate, can be subjected to a series of conversionsto obtain a series of drug molecule precursors or key intermediates, and has wide application prospect.

Despite its significant potential, a general catalytic asymmetric [4+2]-cycloaddition of simple and electronically unbiased dienes with any type of aldehyde has long been unknown. Previously developed methodologies invariably require activated, electronically engineered substrates. We now provide a general solution to this problem. We show that highly acidic and confined imidodiphosphorimidates (IDPis) are extremely effective Br?nsted acid catalysts of the hetero-Diels-Alder reaction of a wide variety of aldehydes and dienes to give enantiomerically enriched dihydropyrans. Excellent stereoselectivity is generally observed and a variety of scents and natural products can be easily accessed.

An unprecedented cascade reaction combining dual iron-amine-catalyzed enantioselective functionalization of allylic alcohols and chemoselective acyl transfer is presented. It allows, from diketones and allylic alcohols, preparation of efficiently function

Aluminium trifluoromethanesulfonate was used as an efficient catalyst for the cycloisomerisation of several unsaturated alcohols into cyclic ethers such as rose oxide and some of its ether analogues.

Ni(acac)2 catalyzes homoallylation of aldehydes with 1,3-dienes in the presence of triethylborane. Triethylborane serves as a reducing agent delivering a formal hydride to the C2 position of 1,3-dienes, thus generating a formal homoallyl anion species and enabling the novel homoallylation of aldehydes. The reaction proceeds smoothly at room temperature in the absence of any phosphane or nitrogen ligands and is highly regioselective and stereoselective for a wide variety combination of aldehydes and 1,3-dienes: e.g., isoprene and benzaldehyde combine to give a mixture of anti- and syn-1-phenyl-3-methyl-4-penten-1-ol (2.2) in a ratio of 15:1 in 90% yield. Under the conditions, sterically congested aliphatic aldehydes and ketones show low yields. In such cases, diethylzinc serves as a substitute for triethylborane and yields the expected products in good yields with similarly high regio- and stereoselectivity. 1,3-Cyclohexadiene is one exception among 24 kinds of dienes examined and undergoes allylation (not homoallylation) selectively.

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The four stereoisomers of the rose oxide analogue Doremox were prepared in enantiomerically enriched form by enantiospecific bakers' yeast reduction of suitable derivatives and by lipase-mediated kinetic resolution of diol precursors.

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We have explored different aspects of the cyclization capability of alkoxymethyl radicals and report here a full account of our investigations. The required radicals were generated from (phenylseleno)-methyl ethers (e.g., 6), which were prepared from homoallylic or bis-homoallylic alcohols by a two-step process. The alcohols were alkylated with (iodomethyl)tributylstannane. The stannanes were reacted with n-BuLi, and the resulting α-alkoxyanions were trapped with diphenyldiselenide to give the (phenylseleno)methyl ethers, which were stable to chromatography. When treated with tributyltin hydride, in the presence of a radical initiator, these precursors undergo a smooth cyclization to substituted tetrahydrofurans and tetrahydropyrans. Formation of the cyclization product was found to be the primary pathway even at relatively high tin hydride concentration. The diastereoselectivity of this cyclization was comparable to that observed in other radical cyclizations. The cis selectivity in cyclization of 6 increased gradually (up to 11:1) as the reaction temperature was lowered. The cyclization can be used for the synthesis of bicyclic and tricyclic compounds and can be incorporated in systems capable of tandem cyclizations.

Alkoxymethyl radicals, generated conveniently from phenylseleno precursors, cyclize to afford substituted tetrahydrofurans and tetrahydropyrans in excellent yield and with good stereoselectivity.