Vishwakarma Singh

A Simple Synthesis of Annulated Bicyclo (2.2.2)-Octenones

Abstract Bicyclo (2.2.2) octanes disposed with β,γ-unsaturated carbonyl chromophore are versatile intermediates for the synthesis of many carbocyclic structures of current interest1. Recently they have also been shown to have great potential towards synthesis of a variety of natural products2. We became interested in acquisition of functionalized annulated bicyclo (2.2.2) octenones of type 1 (Scheme-1) in connection with an exploratory project on the synthesis of polycyclopentanoids. In this context we recently reported that a trapping of a 2, 4-cyclohexadienone with cyclic dienes provides a facile entry into such ring systems3. We now further report an expeditious one step synthesis of annulated bicyclo (2.2.2) octenones 10–15 (Scheme-1) by trapping the 2, 4-cyclohexadienone 3 with various dienophiles 4–9(Scheme-1).

Studies in the synthesis of polycyclopentanoids: synthesis, oxa-di-π-methane rearrangement of annulated bicyclo[2.2.2]octenones and cyclopropane ring cleavage of tetracyclo[6.3.0.0.0]undecenones

A short, new and general approach for the synthesis of linear polyquinanes having the cis:anti:cis tricyclopentanoidal framework is delineated. The key element of this approach is the photochemical 1,2-acyl shift or oxa-di-π-methane rearrangement of annulated bicyclo[2.2.2]octenones, having β,γ-unsaturated carbonyl chromophoric systems. An efficient method for the synthesis of a variety of annulated bicyclo[2.2.2]octenones via inverse demand π4s+π2s cycloaddition of cyclohexa-2,4-dienones (9-12) with olefins (18-26) is reported. The structure of the adducts has been established through the study of their high-field 1H NMR and 13C NMR spectra and decoupling experiments. Synthesis of tricyclo[5.2.2.02,6]undecadienones (51-57) from readily available adduct 43 has been achieved. Oxa-di-π-methane rearrangement of various chromophoric systems to polyquinanes (60-68) is described. The adduct 32 did not undergo oxa-di-π-methane rearrangement upon sensitized irradiation, while adduct 40 rearranged inefficiently to compound 64. Studies on the cleavage of the cyclopropane ring of the tetracyclic ketones (60, 66, 67 and 73) with formic acid and acetyl methanesulfonate is also reported.

Diels-Alder Cycloaddition: Synthesis and Oxa-di-π-Rearrangement of Tricyclo(5.2.2.02,6)-undecadienone

Abstract A short synthesis of various tricyclo(5.2.2.02 6) undecadienones by Diels-Alder reaction of a 2,4-cyclohexadienone with dienes and their oxa-di π- rearrangement is reported.

Tungstic Acid - Hydrogen Peroxide a Simple Reagent for Oxidation of Cycloocta-1, 5-Diene Preparation of (Z) Cyclooct-5-Ene-trans-1, 2-Diol and 1, 6-Dicarbomethoxy (Z) Hex-3-Ene

Abstract A convenient synthesis of (Z) cyclooct-5-enetrans-1, 2-diol from oxidation of cycloocta-1, 5-diene with H2WO4-H202 is described. The trans-1, 2-diol is further transformed into 1, 6-dicarbomethoxy (Z) hex-3-ene.

Micellar Catalysis TT45 + TT2S Cycloaddition in Aqueous Media

Abstract Micelle catalyzed Diels-Alder reaction of cyclic dienes with various quinones in aqueous media is described. Micellar cycloadditions are remarkably faster and give better yields of the adducts compared to the conventional reaction.

π4s + π2s Cycloaddition: Synthesis and OXA-DI-π-Methane Rearrangement of Annulated Bicyclo (2.2.2) Octenones

Abstract A simple one step synthesis of tricyclo (2.2.2.02,6) tetradecadienones and 5-spiro tricyclo (2.2.2.02,6) undecadienone by trapping of 2,4-cyclohexa-dienone with various dienophiles followed by photochemical oxa-di-π-methane rearrangement of the resulting adducts to polyquinanes is described.

A Convenient Synthesis of Novel Pentacyclo [5.4. 0.02,6 .03,10 .05,9] Undecane-8,11-dione-4-spiro-1-cyclopropane

Abstract An efficient synthesis of the title compound by Diels-Alder cycloaddition of spiro(4.2) heptadiene with p-benzoquinone followed by photochemical ring closure is described.

An Efficient Synthesis of a Novel Pentacyclo [5.4.0.02,6.03,10.05,9] Undecane-8, 11-Dione-4-Spiro-1-Cyclopentane

Abstract An efficient synthesis of the title compound by Diels-Alder cycloaddition of spiro (4.4) nonadiene with p-benzoquinone followed by photochemical ring closure is described.

Studies in Strained Polycyclic Systems: A Simple Synthesis of Novel Heptacyclic Diones:

Abstract A simple synthesis of spirodiones (2)&(3) via n6s+ n2s photocyclization of the Deils-Alder adducts (4)&(5) obtained by reactions of spiro (4,2) heptadiene (6) and spiro (4,4) nonadiene (7) with 1,4- naphtho-quinone in homogeneous and micellar media. A remarkable catalytic effect by micelle on cycloaddition is noted.

Annulated bicyclo[2.2.2]octenones: 9-hydroxy-9-chloromethyl-endo-tricyclo[5.2.2.02,6]undeca-4,10-diene-3-spiro(1′-cyclopropane)-8-one and 12-hydroxy-12-chloromethyl-endo-tricyclo [8.2.2.02,9]tetradeca-13-en-11-one

A single crystal X-ray diffraction study of two annulated bicyclo[2.2.2]octenones has been carried out to establish their precise stereostructures. The compounds, with their crystal data, are:1, 9-hydroxy-9-chloromethyl-endo-tricyclo[5.2.2.02,6]undeca-4,10-diene-3-spiro(1′-cyclopropane)-8-one, C14H15O2Cl, space group P21/c,a=10.540(2),b=9.668(1),c=11.841(4)Å, β=95.67(2)°,Z=4, and2, 12-hydroxy-12-chloromethyl-endo-tricyclo[8.2.2.02,9]tetradeca-13-en-11-one, C15H21O2Cl, space group C2/c,a=20.747(8),b=6.498(1),c=20.525(3)Å, β=93.04(3)°,Z=8. The molecule of1 has endo stereochemistry at the ring junction and the spirocyclopropane ring is proximal to the hydroxyl group. In2, the eight membered ring deviates from a chair conformation and one ring atom is disordered. Crystals of1 and2 contain centrosymmetric dimers formed by C=O...O−H hydrogen bonds.