Intramolecular ketenimine-ketenimine [2 + 2] and [4 + 2] cycloadditions

Bis(ketenimines), in which the two heterocumulenic functions are placed in close proximity on a carbon skeleton to allow their mutual interaction, show a rich and not easily predictable chemistry. Intramolecular [2 + 2] or [4 + 2] cycloadditions are, respectively, observed when both ketenimine functions are supported on either ortho-benzylic or 2,2'-biphenylenic scaffolds. In addition, nitrogen-to-carbon [1,3] and [1,5] shifts of arylmethyl groups in N-arylmethyl-C,C-diphenyl ketenimines are also disclosed.     

An Efficient Synthesis of 2,8-Diazabicyclo[4.3.0]-nonane Derivatives via Intramolecular Cyclization Reaction

Novel 5-functionalized-2,8-diazabicyclo[4.3.0]nonane derivatives 5 were synthesized from epoxide 1 through 4 steps in 46.7～52.6% yield.     

Intramolecular [3+2] cycloadditions of functionalized azomethine ylides

The use of dithiane chemistry to synthesize functionalized azomethine ylides which are then employed in [3+2] cycloaddition chemistry is described. The advantages of this methodology as well as an approach to the lycorenine alkaloid system are presented.     

Intramolecular cycloadditions of bis-o-xylyenes. an extremely short route to [2.2.2]cyclophanes.

Benzocyclobutenes linked by two-carbon bridges undergo flashpyrolytic conversion to [2.2.2]cyclophanes.     

Intramolecular [2 + 2]cycloadditions of dialkylketenes with alkenes. Regiochemistry of intramolecular [2+2]cycloadditions of ketenes with alkenes

Unsaturated dialkylketenes 7a, 7b and 7c undergo intramolecular [2 + 2]cycloadditions to give 8a (45%), 9b (23%) and 9c (45%). Intramolecular cycloadditions of dialkylketenes give higher yields than intramolecular cycloadditions of monoalkylketenes, even though dialkylketenes are less reactive than monoalkylketenes. An intramolecular competition experiment with ketene 17 establishes that trans-alkenes are approximately 33 times more reactive than cis-alkenes in intramolecular cycloadditions. Ketene 36 furnishes 22% of the expected bicyclo[3.2.0]heptanone 37 and 28% of bicyclo[3.1.1]heptanone 38.     

Coordination polymer 4,4,10,10-tetramethyl-1,3,7,9-tetraazaspiro[5.5]undecane-2,8-dione with cobalt(II) nitrate: Synthesis and molecular structure

The coordination polymer of cobalt(II) nitrate with bicyclic bis(urea), 4,4,10,10-tetramethyl-1,3,7,9-tetraazaspiro[5.5]undecane-2,8-dione (Sk) {[Co(C₁₁H₂₀N₄O₂)₂(H₂O), Co(C₁₁H₂₀N₄O₂)₂(H₂O)₂]⁴⁺(NO ₃ ^- )₄} _n (I), is synthesized for the first time, and its atomic structure is determined (CIF file CCDC no. 925792). The crystals of compound I are monoclinic: space group P2/c, a = 26.1284(6), b = 7.1763(2), c = 17.1825(5) Å, β = 105.042(3)°, V = 3111.43(15) ų, ρ_calcd = 1.474 g/cm³, Z = 2. The powder X-ray pattern at 293 K is refined using the Rietveld method to confirm the single-phase character of the obtained sample of powdered compound I: a = 26.1456(9), b = 7.1810(4), c = 17.1997(11) Å, β = 105.016(3)°, V = 3119.0(3) ų. The content of the major phase of compound I in the sample is 100 ± 1%, and impurity phases are absent. The crystal of compound I contains two types of chains oriented along the crystallographic direction [001] with similar structures but differed in the coordination numbers of the cobalt atoms. The Co(1) atom has a coordination number of 5 (trigonal bipyramid), and the coordination number of the Co(2) atom is 6 (octahedron). The nitrate anions are uncoordinated.     

2,8-dithia-1,5-diphosphabicyclo[3,3,0]octan- und 2,8-dithia-1-phospha-5-arsabicyclo[3,3,0]octane-derivate

The reaction of dimercaptoethylphosphane HP(CH₂CH₂SH)₂ with tris (diethylamino)phosphane or tris(diethylamino)arsane leads in high yields to the title compounds.     

Synthesis and structure of 2,5,7,10-tetramethyl-2,4,8,10-tetraazabicyclo[4.4.0]decane-3,9-dione

2,5,7,10-Tetramethyl-2,4,8,10-tetraazabicyclo[4.4.0]decane-3,9-dione, a regioisomer of the previously known 2,5,7,8-tetramethyl-2,4,8,10-tetraazabicyclo[4.4.0]decane-3,9-dione, has been synthesized, and its structure has been established by X-ray diffraction analysis. The bicyclic system of this molecule is formed by two heterocyclescis-annelated through the C(1)-C(6) bond. The relative configurations of the asymmetric centers areS for C(5), andR for C(7). In the monohydrate crystal studied, the molecules are linked by O...H-O_w and O...H-N type H-bonds forming a three-dimensional framework.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 136–138, January, 1995.     

2,8-二甲基-1,7-二氧杂螺[5,5]十一烷的合成

果蝇 ( Tephritidae)对水果生产有严重的危害 .热带果蝇寿命较长 ,具有很强的迁徙能力和繁殖能力 .因此开展果蝇生物防治和控制措施的相关研究具有重要的意义 [1,2 ] .Baker等 [3]发现性成熟的雌B.dorsalis果蝇 ,性腺分泌物中包含有螺环缩酮化合物 2 ,8-二甲基 - 1 ,7-二氧杂螺 [5 ,5 ]十一烷 ( 1 ) .Bactrocera Latifrons( Hendel)果蝇的雄性腺体分泌物中也存在螺环缩酮 1 [4 ] ,另外在 rove甲虫腹梢分泌物中也分离出 1 [5] ,螺环缩酮不仅作为性信息素组分存在于许多果蝇腺体中 ,而且作为结构单元存在于许多复杂的有强烈生理活性的天然…     

A Unique and Convenient One-Step Preparation of Spiro[4.5]deca-6,9-diene-2,8-dione

A facile one-step synthesis of spiro[4.5]deca-6,9-diene-2,8-dione(1) from p-methoxyphenylacetyl chloride via a Friedel-Crafts acylation followed by ring closure is reported.