Unusual annulation reaction of an α,β-unsaturated ketone

An unsusual 2,3 cyclopentaindanone (III) was obtained, presumably as a result of a mixed Michael and Stobbe condensation, in the course of an attempted Robinson annulation.     

Synthesis of polycyano-anions conjugated with an aromatic ring

The synthesis of polycyano-anions, conjugated with an aryl substituent via an ethylene fragment, by the Knoevenagel condensation reaction of aromatic aldehydes with the malononitrile trimer potassium salt is described.     

Unusual insertion of product the reaction of 3,3-dichloropenlanedione with aromatic aldehydes

Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, p. 183, January, 1994.     

Reduction of some D-homosteroids with an aromatic a ring with alkali metals under the conditions of Birch's reaction. II.

Summary 1. The reduction of 3-methoxy-D-homoestra-1, 3, 5(10), 8-tetraen-17a-ol (IV) with alkali metals in the presence of ammonium chloride or alcohol gives, in addition to 8, 9-dihydro derivatives, the 8, 9 and 8, 9-epimers, the structure of which has been shown partly by independent synthesis and partly on the basis of chemical reactions and NMR spectra.2. Hydrolysis of the reduction products has given 19-nor-D-homotestosterone (III) and its 8- and 9, 10-epimers (V) and (VI). The ketols (III) and (V) readily form hydroperoxides in air.3. The reduction of the ethylene ketal of 3-methoxy-D-homoestra-1, 3, 5(10), 8-tetraen-17a-one (XIX) takes place stereodirectively and gives only 8, 9-dihydro derivatives.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 2, pp. 90–100, 1965     

Reduction of some D-homosteroids with an aromatic a ring by alkali metals under the conditions of the birch reaction. I

Summary In the Birch reduction of steroid compounds with a phenylbutadiene grouping, i.e., the ketal of 3-methoxy-^{1, 3, 5(10), 8, 14}-D-homoestrapentaen-17a-one (III), the corresponding ketone (IIIa), and 3-methoxy-^{1, 3, 5(10), 8, 14}-D-homoestrapentaen-17a-ol (VI), 1, 4 addition of the hydrogen takes place first, and is followed by reduction of the aromatic nucleus. In this way, 3-methoxy-^{1, 3, 5(10), 8(14)}-D-homoestratetraenone (XII), ^{4, 8(14)}-19-nor-D-homoandrostadienedione (VIII), and ^{4, 8(14)}-19-nor-D-homoandrostadien-17a-ol-3-one (IX) have been obtained.Khimiya prirodnykh soedinenii, Vol. 1, No. 1, pp. 7–15, 1965     

Microwave-assisted thermal decomposition of formamide: a tool for coupling a pyrimidine ring with an aromatic partner

Rapid and efficient generation of CO and NH₃ in the reaction mixture via microwave-assisted thermal decomposition of formamide may represent a significant improvement over existing methods for coupling a pyrimidine ring with an aromatic partner. This work aims at alerting readers on the probability to observe interesting phenomena and reactions when this very powerful heating mode is associated with thermally unstable reagents.     

Synthesis of steroidal saponins bearing an aromatic E ring

A facile synthetic approach toward the steroidal saponins bearing an aromatic E ring was developed starting from the readily available spirostan saponin.     

Unusual reaction of chloramine-T with araldoximes

Reaction of araldoximes with 4 equiv of chloramine-T in refluxing methanol produces N-(p-tolyl)-N-(p-tosyl)benzamides via addition of 2 equiv of chloramine-T to the intermediate nitrile oxide followed by extrusion of sulfur dioxide.     

Induction of an aromatic six-membered nitrogen ring via cation-pi interaction

Nitrogen clusters have been intensively studied for their potential application as high-energy density materials, but a six-membered nitrogen ring (N6) was not found to be stable and aromatic. To explore the possibility of inducing an aromatic N6 ring via cation-pi interaction, quantum chemistry calculations were performed on the systems of Ca2N6, CaN6, CaN6(2-), N6, and N6(4-) at the B3LYP/6-311+G level. The optimized geometries reveal that the planar structure of the N6 ring is stable only in the Ca2N6 complex. The computed NBO and CHelpG charges demonstrate that the planar N6 moiety in the Ca2N6 complex is almost a 10pi-electron system. The predicted nucleus-independent chemical shift (NICS) values demonstrate that the N6 moiety is aromatic in comparison with the NICS values of benzene. The estimated enthalpy of formation for the Ca2N6 complex is 100.4 kcal/mol for the reaction of 2Ca and 3N2. The binding energy between the Ca2+ cation and the N6(4-) moiety is -1928.8 kcal/mol, with electrostatic interaction serving as the predominant component. When all the calculated results are taken into account, including the planar structure, 10pi-electron system, identical bond length, and negative NICS value of the N6(4-) moiety in the Ca2N6 complex, it is deduced that the alkaline earth metal Ca is capable of inducing an aromatic N6 ring through the cation-pi interaction formed by electron transfer from the Ca atom to the N6 ring.     

The reaction of cysteine with α,β-unsaturated aldehydes

Cysteine adds in a two step reaction to acroleine, crotonaldehyde and 4-hydroxypentenal. The first addition products are the β-cysteinyl-substituted saturated aldehydes 1a, 1b and 3. Only the monoadduct of 3, which is stabilized through intramolecular hemiacetal formation, could be isolated. The derivatives 1a and 1b reacted rapidly with additional cysteine to give the thiazolidine compounds 2a and 2b. Whereas 2a and 2b were the only products even in reactions carried out with a molar ratio of aldehyde : cysteine ≧ 1, ratio < 1 was required to obtain a thiazolidine derivative in reactions with hydroxypentenal. The structures of compound 2a, 2b, 3 and 4 were ascertained by means of UV, IR and NMR measurements, potentiometric titrations, determination of the rate laws and elemental analysis. All adducts are in solution in equilibrium with cysteine and the parent aldehydes. Rate constants for forward and reverse reactions were estimated. The rate of forward reactions increase approx. 10-fold per pH unit in the pH range 2–10.