Palladium-Catalysed Intramolecular Cyclisations of Olefinic Propargylic Carbonates and application to the diastereoselective synthesis of enantiomerically pure (−)-α-thujone

Intramolecular [Pd₂(dba)₃]/tri(2-furyl)phosphine-catalysed (dba = dibenzylideneacetone, PhCH?CHCOCH?CHPh) cyclisations of olefinic propargylic carbonates I provided alk-1-enyl-(3-aza)bicyclo[3.1.0]-hexanes VIII in good yields. A palladium cascade sequence I → II → III → IV → VII → VIII is proposed. Furthermore, chiral propargylic carbonates such as 23 , 24 and 25 allowed diastereoselective formation of bicyclo[3.1.0]hexanes 29 , 30 and 31 , respectively. The first diastereoselective synthesis of the monoterpene, (?)-α-thujone 40 illustrates the potential of the method.     

A novel transformation in the quadrone series

A remakable reaction of the substituted bicyclo [3,3,0] oct-3-ene-2-one ($\text{2e}$) with the sodium enolate of malonic ester is described.     

A facile synthesis of strained bridgehead olefins by a gas-phase elimination reaction

A synthesis of bicyclo[3.3.1]non-1-ene $\text{1}$ and of a 10:1 mixture of bicyclo[4.2.1]non-1(8)-ene $\text{2}$ and bicyclo[4.2.1]non-1(2)-ene $\text{3}$ by gas-phase pyrolysis of the corresponding bridgehead acetates and chlorides is reported.     

Reaction of dicarbonyl compounds with dimethyl 3-ketoglutarate. Influence of steric effects on success of the condensation

The influence of steric factors on the synthesis of substituted bicyclo[3.3.0]octane-3,7 diones $\text{via}$ the condensation of 1,2-dicarbonyl compounds with dimethyl 3-ketoglutarate $\text{2}$ is described.     

Preparation et reactions de Diels et Alder des alcenyl-5(3H)-furannones-2

Isomerization of readily available 5-alkenyl 2-(5$\text{H}$)-furanones 1 generated from aldehydes and propiolate anion to 5-alkenyl 2-(3$\text{H}$)-furanones 2 by base treatment provides a new and convenient access by mild Diels-Alder reaction in water to substituted cyclohexanofuranones.     

The synthesis of a 3-diazobicyclo[2.2.1]Heptan-2-one inhibitor of thromboxane a2 synthetase

The synthesis of a PGH₂ analog 5-$\text{endo}$(2(Z), 6-$\text{exo}$(1E)-3-diazo-5-(7-hydroxy-2-heptenyl)-6-(3-hydroxy-1-octenyl)bicyclo[2.2.1]heptan-2-one 2 is described.     

Valence isomerization of C9H10hydrocarbons: Photochemical reactions of bicyclo [3.2.2] nona-2,6,8-triene and its dihydro-derivatives

The valence isomerization reaction of bicyclo[3.2.2]nona-2,6,8-triene ($\text{2}$), which photoisomerized to two homologues of semibullvalene, was discussed with the photoreactions of its dihydro-dreivatives, bicyclo[3.2.2]nona-6,8-diene ($\text{3}$) and bicyclo[3.2.2]nona-2,6-diene ($\text{4}$).     

E- or Z-selective Horner-Wittig reactions of substituted bicyclo[3.3.0]octane-3-ones with chiral phosphonoacetates

The Horner-Wittig reaction of substituted bicyclo[3.3.0]octane-3-ones with chiral phosphonoacetates 2 gave the corresponding unsaturated esters in $\text{E}$/$\text{Z}$-ratios of up to 91 : 9.     

Acid catalyzed isomerization of large ring bicyclic alkenes: a reevaluation of some betweenanene synthetic strategy

Acid treatment of $\text{cis}$-bicyclo[10.10.0]docos-1(12)-ene (Ib) affords bicyclo[10.10.0]docos-1-ene ($\text{11}$) as the sole product. Contrary to a previous report, [10.10]betwwenanene (IIb) is not produced under acidic conditions. Attempts to convert cycloalkylidenecycloalkanes and spiro systems to fused ring alkenes by acid treatment were also unsuccessful.     

The reaction of difluorocarbene with quadricyclane

The reaction of quadricyclane with difluorocarbene to give $\text{endo}$-6-(2,2-difluoro-vinyl)bicyclo[3.1.0]hex-2-ene (4) along with previously reported minor products is described and compared with earlier work.     

Synthesis of Bicyclo[2.2.1]heptan-2-ones by thermal cyclization of 3-allylcyclopentanones

Pyrolysis of 3-allylcyclopentanones affords $\text{endo}$-6-substituted bicyclo[2.2.1]heptan-2-ones.     

An efficient method for selective amino acid protection of meso-2,2′-diaminodicarboxylic acid: An improved synthesis of FK-156

An efficient method for selective amino acid protection with proper differentiation between the two amino acid groups in meso-2,2′-diaminopimelic acid has been achieved [$\text{7}$ → $\text{8}$ → $\text{9}$ → $\text{10}$ → $\text{11}$] and applied to the synthesis of FK-156 [$\text{10}$ → $\text{12}$ → $\text{14}$ → $\text{1}$].     

Cubyl-caged systems: regiochemical steering of cationic rearrangements by distal groups

Novel carbonium ion rearrangements of substituted 1,3-bishomocubanones $\text{3}$ & $\text{4}$ to tricyclo(4.2.0.0^3,8)octane and bicyclo(3.2.1)octane ring systems are reported.     

Comparison of cationic rhodium and iridium complexes in directed homogeneous hydrogenation

The hydrogenation of $\text{endo}$-6-methylenebicyclo[2,2,2]octan-2-ol catalysed by a range of rhodium and iridium complexes has been investigated. Unlike the corresponding $\text{exo}$-alcohol, reduction is highly stereoselective leading to 95 – 99.7% of $\text{endo}$-exo-6-methylbicyclo[2,2,2]octan-2-ol. Selectivity is much less pronounced for the corresponding methyl ether. Rhodium catalysts promote a competitive isomerisation of the double bond to $\text{endo}$-6-methyl-bicyclo[2,2,2]oct-5-en-2-ol, of which an authentic sample was reduced in high yield to pure $\text{exo}$-$\text{endo}$ product. Reduction of both $\text{endo}$-hydroxy substrates by iridium complexes is rapid and highly selective.NMR studies employing europium shift reagents played a central part in defining the stereochemical interrelationships of 2,6-disubstituted bicyclo[2,2,2]octanes.     

Stekeospecific transformation of D-sugar to L-sugar in complex aminoglycoside. Synthesis of a kanamycin B analog having 2,6-diamino-2,4,6-trideoxy-L-arabino-hexopyranose

A 4′-ene derivative of kanamycin B ($\text{4}$) was derived from the epoxide ($\text{1}$) by oxidative elimination of the 4′-phenylseleno group into the allylic alcohol ($\text{3}$). The title compound, 0-(2,6-diamino-2,4,6-trideoxy-β-L-arabino-hexopyranosyl)-(1→4)-0-[3-amino-3-deoxy-α-D-glucopyranosyl-(1→6)]-2-deoxystreptamine ($\text{6}$) was obtained from $\text{4}$ by stereospecific hydrogenation followed by removal of the masking groups, changing the D-sugar moiety of the 4-0-glycoside portion into an L-sugar.     

Condensed cyclic and bridged-ring systems : part 12: A novel synthetic route to 4-p-methoxyphenyl-bicyclo[ 2.2.2 ]octan-2-ones and some bicyclo [ 3.2.1 ] octane derivatives by acid-catalyzed intramolecula

The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{5}$) and 4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{6}$) from easily accessible starting materials. The carbinol $\text{20}$, derived from $\text{5}$, undergoes facile rearrangement leading to 1-$\text{p}$-methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene ($\text{22}$), which has been transformed to $\text{endo}$-1-$\text{p}$-methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one ($\text{25}$).     

Convenient approaches to heterocycles via copper-catalysed additions of organic polyhalides to activated olefins

An efficient method for the synthesis of 2,3-dichloro-5-substituted (Cl, CF₃, alkyl) pyridines $\text{29}$ starting from the 1:1 adducts of the copper-catalysed addition of chloral or the corresponding 2,2-dichloroaldehydes to acrylonitrile is presented. Proper choice of experimental conditions allows the preparation of $\text{29}$ in a one-pot process. Similarly, the CuCl-catalysed reaction of methyl itaconate with several trichloromethyl compounds R-CCl₃ gives 6-R-substituted 2-pyrone derivatives $\text{40}$ via dehalogenation and subsequent thermal ring closure of the primary 1:1-adducts. The new electrophilic 2-pyrone $\text{40b}$ undergoes [4+2]-cycloaddition reactions with inverse electron demand with a number olefins and acetylenes, allowing thereby regioselective transfer of a trifluoromethyl group from a simple Freon derivative (1,1,1-trichloro-2,2,2-trifluoroethane) into more complex organic molecules. Finally, the 1:1-adduct of trichloroacetylchloride with methyl acrylate allows a very convenient synthesis of novel N-substituted derivatives $\text{66}$ of pyroglutamic acid as well as of proline.     

Diastereoselection in the reactions of thioallylic anions with benzaldehyde

Reactions of the anions of (Z)-2-alkenyl N,N-dimethyldithiocarbamates with benzaldehyde gave the $\text{erythro}$ isomers of 4-hydroxy-4-phenyl-(E)-1-alkenyl N,N-dimethyldithiocarbamates stereoselectively and those of the anions of (E)-2-alkenyl N,N-dimethyldithiocarbamates afforded the $\text{threo}$ isomers predominantly.     

Trifluoroacetoxy-phenylselenation of nitroolefins regioselective preparation of nitroallylic alcohol derivatives and their use as multiple coupling reagents

It has been shown In previous papers that the pivalate of 2-nitro-2-propen-1-ol (NPP, $\text{1}$), a nitroolefin with allylic leaving group, can be used as a versatile multiple coupling reagent. The present contribution describes the preparation of NPP analogues, substituted in the 1- and/or 3-position of the allylic carbon skeleton. Standard methods of nitroaliphatic chemistry readily provide symmetrically substituted derivatives such as the cyclohexenes ($\text{7}$) and the indenes ($\text{8}$), while unsymmetrical ones such as the phenyl NPP $\text{9}$ are not so easy to prepare. This situation is now greatly improved by a regioselective method of introducing an allylic pivaloyloxy group into nitroolefins: in the first step of the four-step sequence a phenylseleno- and a trifluoroacetoxy-group are added across the nitroolefinic double bond ($\text{10}$ → $\text{11}$), then, the trifluoroacetate is cleaved, and tne resulting nitro-phenylseleno-alcohol $\text{12}$ is oxidized with elimination to the nitroallylic alcohols $\text{13}$. These are pivalated by pivalic anhydride/ BF₃· etherate (→ $\text{14}$). - The regioselective preparation of the products $\text{16}$–$\text{34}$ of nitroallylation of various nucleophiles with substituted NPP-type reagents demonstrates the broad scope of these multiple coupling reagents. Due to the multitude of conversions of the nitro group, these reagents provide access to a great variety of structures without NO₂ -substituents, cf. $\text{2}$ and $\text{3}$. The mechanism of the reaction of NPP-derivatives is discussed.     

Biomimetic reactions of germacrenes

The biomimetic reactions of epoxygermacrene-D ($\text{1}$) with basic alumina afforded three new interesting compounds ($\text{4}$, $\text{5}$, and $\text{6}$), two of which ($\text{4}$ and $\text{6}$) have the same carbon skeleton as that of periplanone-A ($\text{3}$), a sexual stimulant for the American cockroach. The remaining one ($\text{5}$) is a bicyclo[3.1.0]hexane derivative, from whch an axisonitrile-3 type compound ($\text{14}$) has been produced. Finally, preisocalamendiol ($\text{2}$) was also converted into $\text{6}$.