Yoshiaki Inamoto

Stereospecific Hydroformylation of endo-Dicyclopentadiene in the Presence of Rhodium Complex Catalysts. A Route to endo-Tricyclo[5.2.1.02,6]Dec-8-exo-Ylcarbinol, Precursor of 4-Homoisotwistane

Abstract Since the discovery of a potent antiviral activity of 3-amino-4-homoisotwistane (tricyclo [5.3.1.0]undecane, VIII) our efforts have been directed to find out better methods of synthesizing the parent hydrocarbons. In this communication is reported synthesis of a new precursor to 4-homoisotwistane (VIII), endo-tricyclo [5.2.1.0]dec-8-exo-ylcarbinol (IIIx), via hydroformylation of endo-dicyclo-pentadiene (endo-tricyclo [5.2.1.0]deca-3,8-diene) (I) in the presence of rhodium complex catalysts.

Acid catalyzed ring contractions in endo-2,8-trimethylene-cis-bicyclo[3.3.0]octyl cations to methylperhydrotriquinacenes. One of the methyl ext

Abstract Sulfuric acid catalyzed ring contractions with extrusion of a methyl group were examined for alcohol and olefin derivatives ( 28 – 31 ) of endo -2,8-trimethylene- cis -bicyclo[3.3.0]octane ( 11 ), which was one of the two possible progenitors, among altogether 69 isomers, for methylperhydrotriquinacenes ( 6, 7 and 12 ), the only methyltricyclodecane intermediates found so far, in the tricycloundecane rearrangement. Only minor amounts (1.6–2.0%) of methylperhydrotriquinacenes were formed from these reactants 28–31 , and the results support the earlier theoretical conclusion that the methyl extrusions were in general energetically quite unfavorable processes owing to the formation of primary carbinyl cations at the expense of more stable secondary bridge or tertiary bridgehead ones. Reaction pathways for these precursors 28 – 31 were discussed with reference to those of perhydrotriquinacene 2-carbinyl cations ( 33as ), which corresponded to some of the ring contraction product cations from 28 – 31 .

Application of force field calculations to organic chemistry. Part 7. Steric interpretation of thermolysis, homoketonization, ring enlargement, and acid-catalysed rearrangement of strained cage molecules

Empirical force field calculations are applied to elucidate various types of reaction mechanisms for strained cage molecules. Rates of novel thermal decarbonylation in homologous series of homocubanone derivatives (1; R = phenyl) increase with the calculated strain of the C(2)–C(3) bond, which in turn is strongly influenced by the length of alkylene bridge X, two bonds away from the C(2)–C(3) bond. The remarkable sensitivity of the rates on the calculated C(2)–C(3) bond strain is interpreted in terms of a reactant-like transition state. In contrast, thermolyses, homoketonizations, cationic ring enlargements, and anionic rearrangements of birdcage and homocubyl systems are shown to proceed through product-like transition states based on highly selective formation of the thermodynamically most stable product. The most favourable pathway is presented for a novel acid-catalysed multi-step rearrangement of a bisethanocubanedione derivative (29) to a bisnordiamantanedione derivative (30) based on enthalpy calculations of the intermediate carbonium ions. The failure to produce the ‘stabilomer’ upon acid treatment of (29) under ordinary conditions is attributed to the absence of a mechanistically acceptable path for further skeletal isomerization.

Plant growth retardant activity of 4-homoisotwistane derivatives☆

Abstract A variety of simple derivatives of 3-substituted 4-homoisotwistane derivatives were prepared, and their effect on the growth of cucumber seedlings in complete darkness was investigated. The 3-hydroxy derivative was found to show a strong inhibitory activity at 50 μg/ml, so a series of other hydroxy derivatives of 4-homoisotwistane, endo-2-, exo-2-, and 5-hydroxy- and exo-2,3-dihydroxy-4-homoisotwistane were prepared in order to obtain information on structure-activity relationships. The endo-2-hydroxy derivative inhibited the growth of cucumber and the germination of lettuce seed at 12.5 μg/ml. All the hydroxy derivatives tested increased the number of adventitious roots in hypocotyls of kidney bean at 100 μg/ml, but they inhibited root formation at the lowest part of the cuttings, and the effect was again exhibited most strongly by the endo-2-hydroxy compound. It is suggested that the 2- and 3-hydroxy derivatives possess a potent activity as plant growth retardants.

Application of force field calculations to organic chemistry. Part 6. Steric analysis of synthesis and structure of 1,4-dihydroxytricyclo-[6.4.0.0]dodecane-7,10-dione. Dynamic conformational calculations of its hydrocarbon skeleton and related systems (bicyclo[3.3.1]nonane and bicyclo[3.3.2]decane)

The product distribution for the double intramolecular condensation of cyclododecanetetraone (3) has been calculated by the MM1 force field and found to explain the unexpected isolation of 1,4-dihydroxytricyclo[6.4.0.0,]dodecane-7,10-dione (1). Essential features of the detailed molecular structure of (1), as revealed by a previous X-ray analysis, can be reproduced by this force field. The hydrocarbon framework (9) of (1), which can be regarded as a triply fused twist-chair cyclohexane, an ethano-bridged cis-decalin, or a trimethylene-bridged bicyclo[3.3.1]nonane, was subjected to detailed static and dynamic conformational calculations by the MM2 force field and recognized to be in a deep energy well as is bicyclo[3.3.1]nonane. Similar calculations on the homologue bicyclo[3.3.2]decane reveal that a boat chair conformation (13c) with an eclipsed two-carbon bridge and a twin twist-chair (13a) with a staggered bridge coexist at equilibrium.

Hydride Transfer Reduction-Rearrangement of 5,6-exo-Trimethylene-2-Norbornylcarbinols. A Convenient Synthesis of 4-Homoisotwistane

Abstract 4-Homoisotwistane (tricyclo [5. 3. 1. 03, 8] undecane) (I) has been shown to be one of the most stable intermediates in adamantane rearrangement of various tricycloundecane precursors.1–6 It was also indicated in our experiments that proper choice in precursors and catalysts resulted in almost exclusive formation of 4-homoisotwistane.3–5 Thus isomerization of 2,3-trimethylenebicyclo [2. 2. 2] octane (tricyclo [5. 2. 2. 02,6] undecane) (II) in excess 95% sulfuric acid offered an effective method of synthesizing 4-homoisotwistane.7

Syntheses of ortho-Adamantylphenols

Abstract Reactions of 1-haloadamantane with aromatic compounds such as benzene, toluene, bromobenzene and so on in the presence of Friedel-Craft type catalysts to afford adamantyl-(1)-benzene derivatives have been reported1 already, but little is known about the reaction with phenolic compounds, the only example being the synthesis of 1,3-bis-(p-hydroxyphenyl)-5,7-dimethyl-adamantane by the reaction of 1,3-dibromo-5,7-dimethyladamantane and phenol reported in a patent literature.2

Plant growth retardant activity of polycycloalkanols structurally related to 4-howoisotwistanols

Abstract Various polycycloalkanols structurally related to the plant growth retardants, 4-homoisotwistanols, were prepared and their effect on the growth of cucumber seedlings in complete darkness investigated in order to obtain information on structure-activity relationships. 4-Homobrendan-2-ols, bicyclo[3.3.1]-nonan-1-ol and adamantan-1-ol showed almost the same inhibitory activity as the 4-homoisotwistanols, but 4-homobrendan-3-ol and bicyclo-[3.3.1]nonan-2-ol were only moderately active or almost inactive. No simple relationship was apparent between structure and activity.

Functionalizations and bridgehead reactivity of 4-homoisotwistane (tricyclo[5,3,1,03,8]undecane). Synthesis of 3-substituted derivatives

Bromination and hydride transfer-carboxylation of 4-homoisotwistane (tricyclo[5,3,1,03,8]undecane)(I) to give the 3-substituted derivatives (II) and (III) as well as ready hydrolysis of the 3-bromide (II) shows the high reactivity of the 3-bridgehead in the hydrocarbon (I).

Dehydrobromination of 3-bromotricyclo[5.3.1.03,8]undecane (3-bromo-4-homoisotwistane) and some addition reactions of tricyclo[5.3.1.03,8]-undec-2-ene. Stereochemistry of the formation and reaction of an anti-Bredt compound probed by deuterium substitution

3-Bromotricyclo[5.3.1.03,8]undecane (2) is easily dehydrobrominated with sodium amide in refluxing toluene to give tricyclo[5.3.1.03,8]undec-2-ene (3), an anti-Bredt compound, in 52% yield. The olefin (3) obtained from the 2-exo-deuterio-derivative of the bromo-compound (2) was almost free from deuterium, indicating a predominant exo,syn-mechanism for dehydrobromination. Both acid-catalysed addition of water and oxymercuration of (3) proceeded highly regioselectively with exclusive formation of the 3-alcohol (4), whereas hydroboration of (3) proceeded with less regioselectivity. Use of deuteriated reagents for hydration and oxymercuration–demercuration of (3) and subsequent conversion of the product alcohol (4) into the olefin (3)via the bromide (2) revealed that water underwent addition with an almost pure exo,syn-mechanism, whereas mercury(II) acetate reacted with a mixed syn- and anti-mechanism. The predominant factor in determining the stereochemistry (complete exo,syn) of the acid-catalysed hydration of (3) is suggested to be electronic in nature, consisting of an uneven distribution of π-electrons between the exo- and endo-sides of the olefin (3).