The synthesis of phosphaisocoumarins by Cu(I)-catalyzed intramolecular cyclization of o-ethynylphenylphosphonic acid monoesters

Cu(I)-catalyzed intramolecular cyclization of o-ethynylphenylphosphonic acid monoethyl esters was examined, and a new class of six-membered phosphorus heterocycles was formed with high regioselectivity and good yields. The present reaction is the first example of intramolecular addition of P-OH to alkynes, which provides a convenient way to synthesize novel phosphorus heterocycles having potential bioactivities.     

Ag(I)-catalyzed cyclization reaction of ethyl o-hydroxyphenylethynylphosphinates to phosphachromones

An Ag(I)-catalyzed intramolecular cyclization of ethyl o-hydroxyphenylethynylphosphinate to phosphachromones has been developed with high regioselectivity and good yields. The present reaction represents the first example of intramolecular addition of phenol to 1-alkynylphosphonates, which provides an approach to synthesize new phosphorus heterocycles. The resulting phosphachromones could have potential bioactivities.     

Conformational analysis of 1-sila-4-phospha-2,5-cyclohexadienes

Conformational analysis of 1-sila-4-phospha-2,5-cyclohexadienes was performed using the methods of dipole moments and quantum-chemicall calculations (DFT B3LYP/6-31G*). Irrespective of the degree of coordination of the phosphorus atom (3 or 4) the unsaturated six-membered heterocycles adopt the conformation of a flattened boat with the exocyclic phenyl group oriented perpendicular to the double bonds of the heterocycle. This conformation rules out the possibility of intramolecular transannular interaction between the phosphorus and silicon atoms.     

Ketyl-allene cyclizations promoted by samarium(II) iodide

[reaction: see text] Samarium(II) iodide has proven to be an effective reagent for intramolecular reductive coupling reactions. Previous investigations of intramolecular ketyl-olefin coupling reactions provided carbocycles in excellent yield and good diastereoselectivity. This method has been extended to ketyl cyclizations with allenes. Substrates leading to both carbocycles and heterocycles in a selective manner are explored.     

Phosphorus heterocycles from 2‐(2‐hydroxyphenyl)‐1H‐benzimidazole

Sixteen different P(III) and P(V) heterocycles derived from 2‐(2‐hydroxyphenyl)‐1H‐benzimidazole ( 1 ) are reported. In these heterocycles the phosphorus atom is part of a six‐membered unsaturated ring. They were mainly studied by multinuclear NMR. The X‐ray diffraction of 3,4‐ benzimidazole‐5,6‐benzo‐2‐dimethylamino‐2‐seleno‐ 1,3,2‐oxazaphosphorinane is reported. Phosphoranes derived from 1 and 3,5‐di‐tert‐butylcatechol, and bearing Cl, NMe₂, or phenyl as substituent at phosphorus are presented. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:307–320, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20021     

Intramolecular cyclization of N‐hetarylphosphinimidic isocyanates in the synthesis of 1,7‐dihydro‐4H‐imidazo[4,5‐d][1,3,2]diazaphosphinin‐4‐one (2‐phosphapurine)

It has been found that N‐(4‐imidazolyl)phosphinimidic isocyanates obtained by the reaction of the corresponding chlorophosphine N‐hetarylimide with alkali metal cyanates can undergo intramolecular heterocyclization to yield previously unknown phosphapurine derivatives containing an endocyclic PN double bond. This radically novel approach to building the 2‐phosphapurine system shows promise for the synthesis of related phosphorus‐containing fused heterocycles. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:453–455, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20617     

Formation and Crystal Structure of 4,4'-Oxybis(2,6-bis(dimethylamino)-4H-1,3,5,4-thiadiazaphosphinine 4-Oxide)

Abstract

The reaction of P₄S₁₀ with dimethyl cyanamide as solvent yields a complex mixture of products, from which the new compound 4,4′-oxybis(2,6-bis(dimethylamino)-4H-1,3,5,4-thiadiazaphosphinine 4-oxide) (1) was isolated. In this pyrophosphate derivative, the phosphorus atoms are part of the, otherwise rarely encountered, 1,3,5,4-thiadiaza-phosphinine ring. The molecular structure of the new compound was elucidated by single-crystal X-ray diffraction, showing an almost planar thiadiazaphosphinine ring and a cis-like arrangement of the heterocycles at the two phosphorus atoms.     

Gold(I)-catalyzed intramolecular hydroamination of unactivated alkenes with carboxamides

N-Alkenyl carboxamides undergo gold-catalyzed intramolecular exo-hydroamination to form nitrogen heterocycles in excellent yield.     

Structure of 2,2-bis(trifluoromethyl)-7,7-bis(trifluoromethyl)-hydroxymethyl-1,3,6-trioxaspiro [4.4]non-8-ene

The chemical structure of the unusual condensation product of hexafluoroacetone with 2-hydroxymethylfuran, namely 2,2-bis(trifluoromethyl)-7,7-bis(trifluoromethyl) hydroxymethyl-1,3,6-trioxaspira[4.4]non-8-ene, has been unequivocally established by x-ray structural analysis. The spiroannelated dihydrofuran and dioxalane heterocycles exist in flattened envelope and envelope conformations, respectively. An intramolecular unsymmetrical, bifurcated H-bond is also present.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 64–67, January, 1990.     

Intramolecular hydroamination of alkynes catalyzed by Pd(PPh3)4/triphenylphosphine under neutral conditions

The intramolecular hydroamination of alkynes tethered with amino group 1 in the presence of catalytic amounts of Pd(PPh3)4 and PPh3 in benzene at 100 degrees C proceeded smoothly without the use of any additional acid source to afford five- and six-membered nitrogen heterocycles 2 in good to excellent yields. A compulsory addition of carboxylic acid as a cocatalyst was not needed, and the reaction could be carried out under essentially neutral conditions.     

Substituted diazatetracyclo[4.4.0.1(3,10).1(5,8)]dodecanes as stable caged proton sponges

Herein, we report a molecular framework design differing significantly from the traditional topology of proton sponges. We developed a synthetic approach to the preparation of caged secondary amines by acid-catalyzed rearrangement of fused tetracyclic heterocycles synthesized by intramolecular criss-cross cycloaddition. Alkylation of amines led to air nonsensitive diazatetracyclo[4.4.0.1(3,10).1(5,8)]dodecanes (DTDs) with rare alicyclic scaffolding in high overall yields. Their pK(BH)+ values were determined by transprotonation experiments as well as their sensitivity toward nucleophiles, acids and bases. Crystal structures of free base and monoprotonated form are discussed.     

Highly active Au(I) catalyst for the intramolecular exo-hydrofunctionalization of allenes with carbon, nitrogen, and oxygen nucleophiles

Reaction of benzyl (2,2-diphenyl-4,5-hexadienyl)carbamate (4) with a catalytic 1:1 mixture of Au[P(t-Bu)2(o-biphenyl)]Cl (2) and AgOTf (5 mol %) in dioxane at 25 degrees C for 45 min led to isolation of benzyl 4,4-diphenyl-2-vinylpyrrolidine-1-carboxylate (5) in 95% yield. The Au(I)-catalyzed intramolecular hydroamination of N-allenyl carbamates tolerated substitution at the alkyl and allenyl carbon atoms and was effective for the formation of piperidine derivatives. gamma-Hydroxy and delta-hydroxy allenes also underwent Au-catalyzed intramolecular hydroalkoxylation within minutes at room temperature to form the corresponding oxygen heterocycles in good yield with high exo-selectivity. 2-Allenyl indoles underwent Au-catalyzed intramolecular hydroarylation within minutes at room temperature to form 4-vinyl tetrahydrocarbazoles in good yield. Au-catalyzed cyclization of N-allenyl carbamates, allenyl alcohols, and 2-allenyl indoles that possessed an axially chiral allenyl moiety occurred with transfer of chirality from the allenyl moiety to the newly formed stereogenic tetrahedral carbon atom.     

A highly efficient TBAF-promoted intramolecular cyclization of gem-dibromoolefins for the synthesis of 2-bromobenzofurans(thiophenes)

A highly efficient tetra-(n-butyl)ammonium fluoride (TBAF)-promoted intramolecular cyclization of gem-dibromoolefins has been developed for the synthesis of 2-bromobenzofused heterocycles. The reaction provides a convenient approach to 2-bromobenzofurans(thiophenes) from the corresponding readily available gem-dibromovinyl substrates without a metal.     

1,3-双芳氧乙酰基-1,3,2-二氮磷杂环戊烷-2-硫(硒)代化合物的合成及除草活性研究

利用P(NEt₂)₃与双酰胺类化合物在干馏条件下的环缩合反应合成了一系列含双芳氧乙酰基的新型五元磷杂环,对所合成的化合物进行了元素分析和谱学表征.初步生物活性测定表明,部分化合物具有优良的选择性除草活性.合成中首次发现此类磷杂环的P⁼Se与P-Se的转化现象,通过X射线单晶衍射确证了产物的结构,并发现产物分子间氢键的存在     

Pd(0)-catalyzed oxy- and aminoalkynylation of olefins for the synthesis of tetrahydrofurans and pyrrolidines

The first Pd(0)-catalyzed intramolecular oxy- and aminoalkynylation of nonactivated olefins is reported. The reaction gives access to important tetrahydrofuran and pyrrolidine heterocycles with high diastereoselectivity. The unique synthetic potential of acetylenes is further exploited to access key building blocks for the synthesis of bioactive natural products.     

Acid/base‐catalyzed cyclization of O‐alkynylphenylphosphonic acid monoesters and (O‐hydroxyphenyl)ethynylphosphinates

In this work, we found that acids (i.e., HCl and NaHSO₃) rather than bases could catalyze the cyclization of o‐alkynylphenylphosphonic acid monoesters at slow rates and give phosphaisocoumarins in low to medium yields, whereas the cyclization of (o‐hydroxyphenyl)ethynylphosphinates proceeded very smoothly under basic conditions rather than acidic conditions, and a series of phosphachromones could be prepared in excellent yields at room temperature using K₂CO₃ as catalyst. This is the first example of the synthesis of phosphorus heterocycles via acid/base‐catalyzed intramolecular cyclization of alkynes. Possible mechanisms were discussed. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:649–652, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20728     

Copper(II) acetate promoted intramolecular diamination of unactivated olefins

A concise method for the synthesis of cyclic sulfamides and vicinal diamines is presented. This method is enabled by Cu(OAc)2 and demonstrates a new transformation for this metal. Both five- and six-membered vicinal diamine-containing heterocycles have been synthesized in good to excellent yields, and substrate-based asymmetric induction has been achieved. This is the first reported example of intramolecular diamination of olefins.     

Functionalized cyclopentanes via Sc(III)-catalyzed intramolecular enolate alkylation

We report herein the intramolecular α-tert-alkylation of unsaturated β-ketoesters which gives rise to highly functionalized cyclopentanes. This transformation is characterized by its operational simplicity, mild reaction conditions and the use of scandium (III) triflate as a Lewis acid catalyst. Of interest, cyclopentanes bearing heterocycles, sites for post reaction functionalization and spirocyclic architectures are accessible with this strategy.     

1,3-Diphosphetane-2,4-diyles--Cryptocarbenes?

1,3-Diphosphetane-2,4-diyles ( A ) possess a diradical molecular structure. Experimental studies reveal interconversions of different valence isomers of the diradicals. As a consequence of the facile thermal ring opening of 1,3-diphosphetane-2.4-diyles A , we obtained crypto-phosphinocarbenes ( B ), confirmed by the results of intramolecular rearrangements as well as reactions with multiple bonded systems. A new range of five- and six-membered phosphorus heterocycles are isolated, including transition-metal complexes. The mechanism for the ring-expansion are predicted by quantum chemical calculations.     

Organocatalytic (1+4)-Annulations of MBH Adducts with Electron-Deficient Systems

Benefited from the rapid development of MBH reaction, the reaction of MBH adducts have been established as the most synthetically useful transformations. However, compared with the well-established allylic alkylations and (3+2)-annulations, the (1+4)-annulations of MBH adducts have not developed rapidly until recently. As a helpful complement to the (3+2)-annulations of MBH adducts, the (1+4)-annulations of MBH adducts opens a robust access to structurally diverse five-membered carbo- and heterocycles. This paper summarizes recent advances in organocatalytic (1+4)-annulations using MBH adducts as 1 C-synthons for the construction of functionalized five-membered carbo- and heterocycles.