Synthesis of Functionalized 3-Spiro[cyclopropa[a]pyrrolizine]- and 3-Spiro[3-azabicyclo[3.1.0]hexane]oxindoles from Cyclopropenes and Azomethine Ylides via [3 + 2]-Cycloaddition.

3-Spiro[cyclopropa[a]pyrrolizine]- and 3-spiro[3-azabicyclo[3.1.0]hexane]oxindoles were prepared in moderate to high yields via one-pot three-component reactions using substituted isatins, α-amino acids, and cyclopropenes.

A simple criterion for gas chromatography/mass spectrometric analysis of thermally unstable compounds, and reassessment of the by-products of alkyl diazoacetate synthesis.

Rationale: A principal limitation of gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) is the thermal instability of analytes. We propose that the injector and column temperatures should not exceed the atmospheric pressure boiling point, without decomposition, of the highest homologue of the series being analyzed, instead of the time-consuming procedure of obtaining chromatograms using different temperatures.

Methods: A series of thermally unstable diazocarbonyl compounds, alkyl diazoacetates (predicted limit of stability approx.

Scalable synthesis of (1-cyclopropyl)cyclopropylamine hydrochloride.

1-Cyclopropylcyclopropanecarboxylic acid (2), which is accessible on a large scale (900 mmol) from 1-bromo-1-cyclopropylcyclopropane (1) in 64% yield (89% on a 12.4 mmol scale), has been subjected to a Curtius degradation employing the Weinstock protocol to furnish the N-Boc-protected (1-cyclopropyl)cyclopropylamine 3 (76%). Deprotection of 3 with hydrogen chloride in diethyl ether gave the (1-cyclopropyl)cyclopropylamine hydrochloride (4·HCl) in 87% yield.

Nitrone cycloadditions to 1,2-diphenylcyclopropenes and subsequent transformations of the isoxazolidine cycloadducts.

1,3-Dipolar cycloaddition of C-aryl,N-aryl (or N-methyl) nitrones with a number of 1,2-diphenylcyclopropenes substituted at the C(3) position occurs with the formation of expected "normal" cycloadducts (with N-methylnitrones) and products of their subsequent transformations. Among them are corresponding alpha-acetophenyl aziridines and tetra (or penta) -arylpyrroles. Aziridines and the normal cycloadducts can be also thermally converted to such arylpyrroles with moderate to good yields.

Cyclopropenes in the 1,3-dipolar cycloaddition with carbonyl ylides: experimental and theoretical evidence for the enhancement of sigma-withdrawal in 3-substituted-cyclopropenes.

The carbonyl ylide dipoles generated by the dirhodium tetra-acetate-catalyzed decomposition of diazocarbonyl precursors 1, 5, and 8 cycloadd to 3-substituted 1,2-diphenylcyclopropenes 3a-e and 3,3-disubstituted cyclopropenes 13, 14, 19, and 20 to give polycyclic compounds with 8-oxatricyclo[3.2.1.

The first enantiomerically pure [n]triangulanes and analogues: sigma-[n]helicenes with remarkable features.

(M)-(-)- and (P)-(+)-Trispiro[2.0.0.

trans-1,2,3-Tris(1-hydroxycyclopropyl)cyclopropane.

The central three-membered ring in the title compound, trans-1,1',1"-cyclopropane-1,2,3-triyltris(cyclopropanol), C(12)H(18)O(3), shows pronounced asymmetry of the bond lengths, which is induced by the different orientations of the substituents. A network of hydrogen bonds links the molecules into sheets.

The First Enantiomerically Pure Triangulane (M)-Trispiro.

A remarkably high specific rotation, even at 589 nm, is shown by (M)-1, the first enantiomerically pure unbranched [4]triangulane, although it has no chromophore that would lead to any significant absorption above 200 nm. This outstanding rotatory power is in line with a helical arrangement of its sigma bonds, as confirmed by high-level computations. Thus, it is appropriate to call (M)-1 a "sigma-[4]helicene", the first sigma-bond analogue of the aromatic [n]helicenes.