β-Substituted ketene thioacetals as β-lithioacrylate equivalents. The synthesis of (±)-eldanolide

Lithiation of 1,1-bis(phenylthio)-3-phenylthio-1-propene 3 and reaction with a range of electrophiles gave exclusively the γ-substituted product 4. This reagent has been used in a short synthesis of the pheromone, (±)-eldanolide.     

Functionalized cyclopentanes via radical cyclizations using thiocarbonate derivatives as initiators and terminators

A radical-based cyclization is described that employs xanthates or cyclic thionocarbonates as initiators and allylic dithiocarbonates or allylic thiocarbamates as terminators.     

New Synthesis of ketene thioacetals,vinylsulfides and their seleno analogues

Title compounds have been prepared on reaction of thioacetals, orthothioesters and their seleno analogues with diphosphorus tetraiodide (P₂I₄) or phosphorus triiodide (PI₃).     

Alkylation of metallated ketene thioacetals. Effect of the hardness of the leaving group and electrophile

The harder the leaving group or the Lewis acid end of the alkylating agent, the higher the proportion of C-1 alkylation of lithium ketene thioacetal (6).     

The carboalkoxyallylsilane terminator for biomimetic polyene cyclizations. A route to 21-hydroxyprogesterone types

Polyene 3 containing a carboalkoxyallylsilane terminator was cyclized to give pro-steroid 6 in 68–75% yield. Unequivocal proof for the structure of 6 was obtained by conversion to the racemic form of the natural cortical hormone 17-desoxycorticosterone (15).     

Catalytic use of selenium electrophiles in cyclizations

A new and convenient one-pot method for a catalytic addition-elimination reaction using selenium electrophiles has been developed. In the presence of 5 mol % diphenyl diselenide, [bis(trifluoroacetoxy)iodo]benzene in acetonitrile converted a range of (E)-3-butenoic acids into the corresponding butenolides in good yields.     

Gold(I)-catalyzed regioselective cyclizations of silyl ketene amides and carbamates with alkynes

The gold(I)-catalyzed regioselective cyclizations of silyl ketene amides or carbamates with alkynes were utilized to construct cyclopentanes or dehydro-delta-lactams.     

微波照射下膦酰基/硫甲基烯酮硫代缩醛和N-取代膦酰 基/硫甲基硫代碳酸酯的 合成

在微波照射下方便、高收率地合成了新奇的膦酰基杂环的合成子-膦酰基/硫甲基烯酮硫代缩醛和N-取代膦酰基/硫甲基硫代碳酸酯,实验表明微波照射大大加快了反应速率和提高了反应产率。     

Phosphoryl-substituted 1-azadienes for use in intra-molecular diels-alder cyclizations

The preparation and isolation of 2-(diethoxyphosphoryl)-1-azadienes and their use in the formation of functionalized quinolizidine and indolizidine ring systems via an intramolecular Diels-Alder reaction is described.     

Strategic use of pinacol-terminated Prins cyclizations in target-oriented total synthesis

An important objective of contemporary synthesis endeavors is the development of new transformations that rapidly evolve molecular complexity in a stereocontrolled fashion. One approach toward this goal is to combine two or more distinct reactions into a single transformation, producing a process often referred to as a sequential, tandem, cascade, or domino reaction. In this Perspective, we discuss the development of one such tandem reaction, the acid-promoted (or catalyzed) Prins-pinacol rearrangement, with particular emphasis on its implementation as the key strategic element in the total synthesis of heterocyclic and carbocyclic natural products.     

A new synthesis of β-amino acids by use of ketene diethyl acetal as enolate equivalent

Reaction of phenylsulfonyl formamides, readily available in a single step from an aromatic aldehyde and sodium phenylsulfinate, with ketene diethyl acetal under basic conditions gives N-formyl β-amino acid esters in good yield, which can be kinetically resolved with a lipase.     

Nanoassembly of biocompatible microcapsules for urease encapsulation and their use as biomimetic reactors

Biocompatible polypeptide capsules with high enzyme loading and activity prepared by templating mesoporous silica spheres were used as biomimetic reactors for performing CaCO3 synthesis exclusively inside the capsule interior via urease-catalyzed urea hydrolysis.     

Methylsulfenylation of thioacetals as a method for synthesizing 2-thio-substituted furans

[formula: see text] The dimethyl(methylthio)sulfonium tetrafluoroborate induced cyclization of various bis(methylsulfanyl) carbonyl compounds is described. The reaction proceeds by methylthiolation of the thioacetal group to give a thionium ion which undergoes subsequent cyclization with the neighboring carbonyl group. This is followed by an elimination reaction to furnish the furan ring.     

Oligomers as initiators of free radical polymerization

Methyl methacrylate, benzyl methacrylate, butyl methacrylate, and methacrylic acid can be polymerized by 1, 2, 2-tetraphenyl-1, 2-diphenoxyethane (TPPA), 1, 1, 2, 2-tetraphenyl-1, 2-bis-(trimethylsiloxy) ethane (TPSA), and 1, 1, 2, 2-tetraphenyl-1, 2-dicyanoethane (TPCA) (1–3). The polymerization with these initiators is characterized by three steps; in the first period oligomers from MMA and initiator radicals are formed by primary radical termination.     

Iron-sulfur proteins as initiators of radical chemistry

Iron-sulfur proteins are very versatile biological entities for which many new functions are continuously being unravelled. This review focus on their role in the initiation of radical chemistry, with special emphasis on radical-SAM enzymes, since several members of the family catalyse key steps in the biosynthetic pathways of cofactors such as biotin, lipoate, thiamine, heme and the molybdenum cofactor. It will also include other examples to show the chemical logic which is emerging from the presently available data on this family of enzymes. The common step in all the (quite different) reactions described here is the monoelectronic reductive cleavage of SAM by a reduced [4Fe-4S](1+) cluster, producing methionine and a highly oxidising deoxyadenosyl radical, which can initiate chemically difficult reactions. This set of enzymes, which represent a means to perform oxidation under reductive conditions, are often present in anaerobic organisms. Some other, non-SAM-dependent, radical reactions obeying the same chemical logic are also covered.     

Reactions of ketene acetals-14 The use of simple mixed vinylketene acetals in the annulation of quinones

α,β- β, γ-unsaturated esters can be converted by strong base and chlorotrimethylsilane to the corresponding mixed vinylketene acetals which are shown to be particularly useful and generally applicable reagents for the regiospecific annulation of halogenoquinones. The reaction proceeds readily with a variety of substrates including benzoquinones.