The first one-pot oxidative 1,2-acetoxysulfenylation and 1,2-disulfenylation of Baylis-Hillman alcohols in an ionic liquid

The first example of tandem oxidation and 1,2-acetoxysulfenylation/1,2-disulfenylation of Baylis-Hillman (BH) alcohols to afford 1,2-acetoxysulfides/1,2-dithioethers is reported. The reaction involves oxidation of BH alcohols with IBX in [bmim]Br to give β-ketomethylene compounds in situ followed by CuI-imidazole-catalyzed 1,2-acetoxysulfenylation with an organodisulfide and acetic acid under air to afford vicinal acetoxysulfides in excellent yields with complete regioselectivity. In the absence of the Cu(I) catalyst, 1,2-disulfenylation takes place to give vicinal dithioethers in 81-90% yields.     

Radical additions to 1,2-dichlorodifluoroethene

Fluorine containing alcohols, esters and ethers have been obtained by peroxide induced radical addition of alcohols, esters and ethers to 1,2-dichlorodifluoroethene.The influence of the kind and amount of the peroxide has been studied and the reactivity of alcohols, esters and ethers compared.     

Efficient Preparation of Biologically Important 1,2-Amino Alcohols

An efficient three-step methodology developed for the preparation of 1,2-amino alcohols. In the first step a rapid coupling between bromoketones and potassium phthalimide in ionic liquid produced α-phthalimido ketones in quantitative yields, which is followed by a facile reduction using NaCNBH₃ in acetic acid to give corresponding phthalimido alcohols and finally effecting hydrazinolysis in water at 60 °C to yield biologically important 1,2-amino alcohols.     

Metal-free synthesis of 1,2-amino alcohols by one-pot olefin aziridination and acid ring-opening

A one-pot, two-step reaction comprising olefin aziridination and ring-opening of an aziridine intermediate to synthesize 1,2-amino alcohols has been developed. This reaction is suitable for several types of olefin. This methodology allows an efficient and highly stereoselective approach to various 1,2-amino alcohols, readily providing an alternative route to conventional vicinal amino alcohols.     

1,2-联烯基酮的合成与反应

1,2-联烯基酮可以通过2-丙炔基酮异构化反应,相应有机金属试剂中间体与酯、酰氯或酰胺的反应,[2,3]或[3,3]迁移反应,Wittig反应,消除反应,2,3-联烯醇氧化等方法合成。由于联烯酮上含有吸电子基团羰基,它可发生亲核加成、环加成、环化反应。     

Synthesis of vinyl 1,2-diketones

A new route is outlined for preparation of vinyl 1,2-diketones via a three-step sequence. First, allylic alcohols are photooxidized by ¹O₂ to hydroperoxides, which are reduced to vinyl 1,2-diols. These vinyl 1,2-diols are oxidized to vinyl 1,2-diketones with oxoammonium salts, which are prepared in situ from organic nitroxyl radicals. The new route is short, avoids the use of protecting groups, and is generally applicable to obtain aliphatic or aromatic vinyl 1,2-diketones.     

Straightforward Synthesis of 1,2-Amino Phosphate Diesters and Application to the Synthesis of Novel 1,2-Amino Ether Diesters

A variety of 1,2-amino alcohol diesters 1 reacted smoothly with diethyl chlorophosphate under basic conditions to afford the corresponding 1,2-amino phosphate diesters 2 in excellent yields. These compounds served as useful precursors for subsequent nucleophilic attack by alcohols in an S_N2 fashion to provide 1,2-amino ether diesters 3.     

Regio- and stereospecific syntheses of syn- and anti-1,2-imidazolylpropylamines from the reaction of 1,1'-carbonyldiimidazole with syn- and anti-1,2-amino alcohols

The regio- and stereospecific conversion of syn- and anti-1,2-amino alcohols to their respective syn- and anti-1,2-imidazolylpropylamines via treatment with 1,1'-carbonyldiimidazole is described. The rationale behind the regio- and stereospecific nature as well as the generality of the reaction is discussed.     

Benzotriazolyl-mediated 1,2-shifts of electron-rich heterocycles

The anion formed from the lithiation of 1-[(methylthio)methyl]-1H-benzotriazole 1 with n-BuLi adds to heteroaryl ketones to give 2-benzotriazolyl alcohols 3a-m. Thermolysis of 3a-g in the presence of zinc bromide induces a 1,2-shift of heteroaromatic groups to form ketones 4a-g. By contrast, in the rearrangement of 2-benzotriazolyl alcohols 3h,i,k-m migration of the phenyl group rather than the corresponding heteroaromatic groups occurred to give ketones 4h,i,k-m.     

Synthesis of 1,2- and 1,4-amino alcohols from 1,3-dienes via oxazines. Rearrangements of 1,4-amino alcohol derivatives to oxazolines

Conjugated dienes were converted to 1,2-oxazines by reaction with an acyl nitroso dienophile. The oxazines were reduced to 1,4-N-acetylamino alcohols, which were rearranged to the corresponding oxazolines upon treatment with methanesulfonyl chloride or anhydride. The oxazolines yielded 1,2-N-acetylamino alcohols upon hydrolysis. Thus either 1,4- or 1,2-N-acetylamino alcohols are available from 1,3-dienes via this methodology. Experimental and spectral data are provided for all new compounds.     

Catalyst-free one-pot synthesis of benzimidazoles from 1,2-diaminoarenes and alcohols

A new and efficient protocol is described for the one-pot synthesis of benzimidazoles from a variety of aryl alcohols and 1,2-diaminoarenes. The yields were ranging from moderate to excellent. Moreover, the present method is utilizing alcohols instead of aldehydes and the reactions are carried out under solvent- and catalyst-free conditions, offering an environmentally benign process.     

Stereoselective synthesis of 1,2-disubstituted beta-amino alcohols by nucleophilic addition to N-tert-butanesulfinyl alpha-alkoxyaldimines

N-tert-Butanesulfinyl alpha-alkoxyaldimines are readily prepared from protected (S)-lactals without epimerization at the alpha-stereocenter. Addition of ethyl and phenyl Grignard reagents, as well as the titanium enolate of methyl acetate, to the N-tert-butanesulfinyl aldimines provides 1,2-disubstituted beta-amino alcohols in good yields (73-98%) and with high diastereoselectivities. Either syn- or anti-amino alcohol products can be obtained by the appropriate choice of alcohol protecting groups and/or reaction conditions. Finally, deprotection of the addition products provides straightforward access to either syn- or anti-1,2-amino alcohols.     

Propargyl 1,2-orthoesters as glycosyl donors: stereoselective synthesis of 1,2-trans glycosides and disaccharides

Propargyl 1,2-orthoesters are identified as glycosyl donors. Various glycosides and disaccharides were synthesized in a stereoselective manner using AuBr₃ as the promoter. AuBr₃ may activate the alkyne resulting in the formation of a 1,2-dioxolenium ion and also behaves as a Lewis acid to facilitate the attack of the glycosyl acceptor. The versatility of the protocol was demonstrated using a panel of aglycones comprising aliphatic, alicyclic, steroidal and sugar alcohols.     

New polyhydroxylated pyrrolidines derived from enantiopure 3,6-dihydro-2H-1,2-oxazines

[reaction: see text] Diastereoselective hydroborations of enantiopure 3,6-dihydro-2H-1,2-oxazines led to dihydroxy-substituted 1,2-oxazines. Samarium diiodide-induced N-O bond cleavage generated 1,4-amino alcohols which were recyclized to polyhydroxylated pyrrolidines which are potential glycosidase inhibitors.     

Regioselective and diastereoselective allylic amination using chlorosulfonyl isocyanate. A novel asymmetric synthesis of unsaturated aromatic 1,2-amino alcohols

The diastereoselective synthesis of unsaturated aromatic 1,2-amino alcohols can be achieved on an epimeric mixture of optically active allylic ethers having a hydroxyl group attached to an allylic chiral center to the pi-system using chlorosulfonyl isocyanate. These reactions produced the unsaturated anti-1,2-amino alcohols either exclusively or predominantly only for aromatic derivatives. The anti-selectivity may be explained by the Cieplak electronic model during the conversion from ethers to carbamates.     

Enhancement of 1,2-dehydration of alcohols by alkali cations and protons: a model for dehydration of carbohydrates

We have used electronic structure calculations to investigate the 1,2-dehydration of alcohols as a model for water loss during the pyrolysis of carbohydrates found in biomass. Reaction enthalpies and energy barriers have been calculated for neat alcohols, protonated alcohols and alcohols complexed to alkali metal ions (Li⁺ and Na⁺). We have estimated pre-exponential A factors in order to obtain gas phase rate constants. For neat alcohols, the barrier to 1,2-dehydration is about 67 kcal mol⁻¹, which is consistent with the limited experimental data. Protonation and metal complexation significantly reduce this activation barrier and thus, facilitate more rapid reaction. With the addition of alkali metals, the rate of dehydration can increase by a factor of 10⁸ while addition of a proton can lead to an increase of a factor of 10²³.     

Preparation of an aliphatic-substituted hypervalent iodine compound, tetracoordinate 1,2-iodoxetane 1-oxide, and its application to oxidation

A tetracoordinate 1,2-iodoxetane was prepared by the fluorination of a tricoordinate 1,2-iodoxetane with xenon difluoride followed by hydrolysis. The tetracoordinate 1,2-iodoxetane oxidized alcohols and a sulfide to the corresponding aldehydes and ketones, and a sulfoxide, respectively, in good to moderate yields under mild conditions.     

A highly divergent Pictet-Spengler approach for pyrrolo[1,2-a]quinoxalines from aryl amine using 1,2-dinitrobenzene as an oxidant

A convenient Pictet-Splengler approach for the synthesis of substituted pyrrolo[1,2-a]quinoxalines from aryl amine and 1-(2-aminoaryl)-pyrrole has been developed. This is the first domino protocol involving formation of benzaldehyde as an intermediate from benzyl amines and benzyl alcohols using 1,2-DNB as an oxidant, followed by its endo cyclization with 1-(2-aminophenyl)-pyrrole to furnish the pyrrolo[1,2-a]quinoxalines. Notably, this procedure exhibits good functional group tolerance as well as good to moderate yield of pyrrolo[1,2-a]quinoxaline.     

Indium-mediated consecutive 1,2-shift reaction and regioselective allylation of vinyl epoxides

Allyl indium, prepared from allyl bromide and indium metal in aprotic solvent, reacts with terminal vinyl epoxides at room temperature to afford various bishomoallyl alcohols in moderate to high yields via consecutive 1,2-shift reaction and regioselective allylation.     

One-pot synthesis of 1,2-dihydropyridines: expanding the diverse reactivity of propargyl vinyl ethers

The catalyzed synthesis of 1,2-dihydropyridines starting from easily accessible propargyl vinyl ethers was realized. The reaction sequence involving a transition metal-catalyzed propargyl-Claisen rearrangement, a condensation step, and a Br?nsted acid-catalyzed heterocyclization furnishes the highly substituted heterocycles in moderate to excellent yields. Additionally, a practical one-pot protocol toward 1,2-dihydropyridines and 2H-pyrans starting from propargylic alcohols was developed.