A Light-Induced Vinylogous Nazarov-Type Cyclization

The first examples of a photochemically induced vinylogous Nazarov-type cyclization forming a cycloheptadienone core are described. The reaction can be included in a three-step cascade consisting of a photochemical isoxazole–azirine ring contraction, cobalt­(II)-catalyzed ring expansion, and the photochemical cyclization. Furthermore, the first representative of the hitherto unknown 1-azatricyclo­[2.2.0.0^2,6]­hexanes has been identified as a side product of the azirine formation

A Light-Induced Vinylogous Nazarov-Type Cyclization

The first examples of a photochemically induced vinylogous Nazarov-type cyclization forming a cycloheptadienone core are described. The reaction can be included in a three-step cascade consisting of a photochemical isoxazole–azirine ring contraction, cobalt­(II)-catalyzed ring expansion, and the photochemical cyclization. Furthermore, the first representative of the hitherto unknown 1-azatricyclo­[2.2.0.0^2,6]­hexanes has been identified as a side product of the azirine formation

Intramolecularly Coordinated Bis(crown ether)-Substituted Organotin Halides as Ditopic Salt Receptors

The synthesis of the bis­(crown ether)-substituted organostannanes X₂Sn­(CH₂-[16]-crown-5)₂ (<b>3</b>, X = I; <b>4</b>, X = Br; <b>5</b>, X = Cl; <b>6</b>, X = F) and X₂Sn­(CH₂-[13]-crown-4)₂ (<b>10</b>, X = I; <b>11</b>, X = Br; <b>12</b>, X = F) is reported. The compounds have been characterized by ¹H, ¹³C, ¹⁹F, and ¹¹⁹Sn NMR spectroscopy, elemental analyses, and electrospray ionization mass spectrometry (ESI-MS). Single-crystal X-ray diffraction analyses reveal a distorted-octahedral <i>cis</i>,<i>cis</i>,<i>trans </i>configuration of the tin atoms in compounds <b>4</b>–<b>6</b> and <b>10</b>–<b>12</b> as a result of intramolecular O→Sn coordination. The ability of the host molecules to form mono- and ditopic complexes with various halide salts in different solvents, including water, has been investigated by NMR spectroscopy and ESI-MS

Cyclic Dinuclear Organotin Cations Stabilized by Bulky Substituents

The syntheses of sterically congested 2,2-bis­(diorganochloridostannyl)­propane, Me₂C­(SnClR₂)₂ (<b>1</b>; R = CH­(SiMe₃)₂), the related salts [cyclo-{Me₂C­(SnR₂)₂X}­B­(Ar^F)₄] (<b>2</b>, X = Cl; <b>3</b>, X = OAc; <b>4</b>, X = OH; Ar^F = 3,5-(CF₃)₂C₆H₃), and the four-membered-ring cyclo-{Me₂C­(SnR₂)₂O} (<b>5</b>) are reported. The compounds have been characterized by elemental and EDX analyses, ¹H, ¹¹B, ¹³C, ¹⁹F, ²⁹Si, and ¹¹⁹Sn NMR and IR spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction analysis

Novel Stannatrane N(CH₂CMe₂O)₂(CMe₂CH₂O)SnO-<i>t-</i>Bu and Related Oligonuclear Tin(IV) Oxoclusters. Two Isomers in One Crystal

The syntheses of the alkanolamine N­(CH₂CMe₂OH)₂(CMe₂CH₂OH) (<b>1</b>), of the stannatrane N­(CH₂CMe₂O)₂(CMe₂CH₂O)­SnO-<i>t-</i>Bu (<b>2</b>), and of the trinuclear tin oxocluster <b>3</b> consisting of the two isomers [(μ₃-O)­(O-<i>t</i>-Bu)­{Sn­(OCH₂CMe₂)­(OCMe₂CH₂)₂N}₃] (<b>3a</b>) and [(μ₃-O)­(μ₃-O-<i>t</i>-Bu)­{Sn­(OCH₂CMe₂)­(OCMe₂CH₂)₂N}₃] (<b>3b</b>) as well as the isolation of a few crystals of the hexanuclear tin oxocluster [LSnOSn­(OH)₃LSnOH]₂ [L = N­(CH₂CMe₂O)₂(CMe₂CH₂O)] (<b>4</b>) are reported. The compounds were characterized by ¹H, ¹³C, ¹⁵N, and ¹¹⁹Sn (<b>1–3</b>) nuclear magnetic resonance and infrared spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction analysis (<b>1–4</b>). A graph set analysis was performed for compound <b>1</b>. The relative energies of <b>3a</b> and <b>3b</b> were estimated by density functional theory calculations that show that the energy differences are small

Iodocyclization of <i>o</i>‑Alkynylbenzamides Revisited: Formation of Isobenzofuran-1(3<i>H</i>)‑imines and 1<i>H</i>‑Isochromen-1-imines Instead of Lactams

The iodocyclization of <i>o</i>-alkynylbenzamides with various electrophiles has been reported to yield five- or six-membered lactams by nucleophilic attack of the amide nitrogen onto the triple bond. While the formation of an isobenzofuran-1­(3<i>H</i>)-imine with two bulky substituents under Larock conditions was initially attributed to steric hindrance, we found out that cyclization via the amide oxygen is the rule rather than the exception. Thus, the structures of the products reported in the literature need to be revised

Iodocyclization of <i>o</i>‑Alkynylbenzamides Revisited: Formation of Isobenzofuran-1(3<i>H</i>)‑imines and 1<i>H</i>‑Isochromen-1-imines Instead of Lactams

The iodocyclization of <i>o</i>-alkynylbenzamides with various electrophiles has been reported to yield five- or six-membered lactams by nucleophilic attack of the amide nitrogen onto the triple bond. While the formation of an isobenzofuran-1­(3<i>H</i>)-imine with two bulky substituents under Larock conditions was initially attributed to steric hindrance, we found out that cyclization via the amide oxygen is the rule rather than the exception. Thus, the structures of the products reported in the literature need to be revised

Iodocyclization of <i>o</i>‑Alkynylbenzamides Revisited: Formation of Isobenzofuran-1(3<i>H</i>)‑imines and 1<i>H</i>‑Isochromen-1-imines Instead of Lactams

The iodocyclization of <i>o</i>-alkynylbenzamides with various electrophiles has been reported to yield five- or six-membered lactams by nucleophilic attack of the amide nitrogen onto the triple bond. While the formation of an isobenzofuran-1­(3<i>H</i>)-imine with two bulky substituents under Larock conditions was initially attributed to steric hindrance, we found out that cyclization via the amide oxygen is the rule rather than the exception. Thus, the structures of the products reported in the literature need to be revised

Iodocyclization of <i>o</i>‑Alkynylbenzamides Revisited: Formation of Isobenzofuran-1(3<i>H</i>)‑imines and 1<i>H</i>‑Isochromen-1-imines Instead of Lactams

The iodocyclization of <i>o</i>-alkynylbenzamides with various electrophiles has been reported to yield five- or six-membered lactams by nucleophilic attack of the amide nitrogen onto the triple bond. While the formation of an isobenzofuran-1­(3<i>H</i>)-imine with two bulky substituents under Larock conditions was initially attributed to steric hindrance, we found out that cyclization via the amide oxygen is the rule rather than the exception. Thus, the structures of the products reported in the literature need to be revised

Iodocyclization of <i>o</i>‑Alkynylbenzamides Revisited: Formation of Isobenzofuran-1(3<i>H</i>)‑imines and 1<i>H</i>‑Isochromen-1-imines Instead of Lactams

The iodocyclization of <i>o</i>-alkynylbenzamides with various electrophiles has been reported to yield five- or six-membered lactams by nucleophilic attack of the amide nitrogen onto the triple bond. While the formation of an isobenzofuran-1­(3<i>H</i>)-imine with two bulky substituents under Larock conditions was initially attributed to steric hindrance, we found out that cyclization via the amide oxygen is the rule rather than the exception. Thus, the structures of the products reported in the literature need to be revised