Reactions of thioketen s-oxides with diazo compounds : A novel synthesis of heterocyclic sulfines

Thioketen S-oxides 1 react with 2-diazopropane (2a) to give 1-pyrazoline-4-thione S-oxides 3 Addition of diazomethane to 1 yields a stable 1:1-adduct only from the S-oxide 1c. The constitution of both types of cycloadducts (3, 11) was proven by X-ray diffraction. Irradiation of 3 leads to loss of nitrogen to afford the alkylidene thiirane S-oxides 12.     

Halogen addition to - and -tricyclo[5.2.1.0]deca-4,8-dien-3-ones

The reactions of endo- and exo-tricyclodecadienones and with bromine and iodine are described. The chemo- and regioselectivity of these additions depend on the nature of both reagent and substrate and are explained in terms of the configuration of the tricyclic compounds and the general mechanism for electrophilic halogenation. From a synthetic point of view only the bromination of endo-tricyclodecadienone is useful. Other reactions fail ( with I₂), result in addition to the norbornene double bond ( with I₂) or give rise to complex mixtures ( and with Br₂).     

Approach to the perhydroisoindole system in cytochalasin B

The synthesis of the perhydroisoindole systems 17a, b, 22 and 23 is described using the following sequence of reactions. Diels-Alder cycloaddition of silyloxydienes 4 with methyl acrylate leads, after methanolysis, to cyclohexenonecarboxylates 6, subsequent acetalization and epoxidation of the α,β-unsaturated esters 7 yields the epoxy esters 8 and 9. Conversion of these esters into acyl chlorides 11, via the sodium salts 10, and subsequent treatment with an amine component (phenylalanine methyl ester, diethyl aminomalonate and ethyl 2-amino benzoyl-acetate) produces the epoxy carbonamides 12, 15 and 18, respectively. These epoxy amides are subjected to acid-catalyzed hydrolysis to give the cyclohexenonecarbonamides 13, 16 and 19, respectively. Subsequent ring-closure of the amides 16 and 19 with base leads to the perhydroisoindole derivatives 17a, b and 22, respectively. The formation of 22 proceeds via a concomitant benzoyl transfer reaction. The amide 13 failed to ring-close. A by-product of the acid treatment of 18 is 21 which with base undergoes a benzoyl transfer to perhydroisoindole 23. The structures of the products 9a, 22 and 23 were ascertained by means of an X-ray analysis.     

Coordination chemistry of sulfines : I. Synthesis and characterization of the complexes Pt(PPh3)2(XYCSO) (X,Y = aryl,S-aryl,S-alkyl,Cl). Coordination via the CS-π-bond

Reactions of Pt(PPh₃)₄ with the sulfines, XYCSO, (X, Y = aryl, S-aryl, S-alkyl, Cl) yield coordination compounds of the type Pt(PPh₃)₂(XYCSO). Infrared, ³¹P and ¹H NMR spectra reveal that in all cases the sulfine ligand is coordinated side-on via the CS π-bond (Pt—η²-CS). Reactions of Pt(PPh₃)₄ with either the E- or Z-isomer of (p-CH₃C₆H₄)(CH₃S)CSO yields the corresponding E- or Z-coordination compound, Pt(PPh₃)₂[E-(p-CH₃C₆H₄)(CH₃S)CSO] or Pt(PPh₃)₂[Z-(p-CH₃C₆H₄)(CH₃S)CSO], indicating that the configuration of the sulfine ligand is retained upon coordination to the Pt(PPh₃)₂ unit. The compounds Pt(PPh₃)₂(XYCSO), containing reactive CX and/or CY bonds (X, Y = S-aryl, S-alkyl, Cl), undergo a rearrangement in solution to give complexes of the type PtX(PPh₃)₂(YCSO).     

Nucleophilic eliminative ring fission of bridgehead substituted 1,3-bishomocubyl acetates

The base induced cage fission of three different types of functionalized bridgehead substituted 1,3-bishomocubyl acetates, vizA,B and C is described. The synthesis of two 6-functionalized 1,3-bishomocubyl 4-acetates (type A), viz4-acetoxypentacyclo[5.3.0.0^2,5.0^3,9.0^4,8]decan-6-one 5 and its ethylene acetal 6 has been accomplished starting from the readily available Diels-Alder adduct 4. The synthesis of three 1,3-bishomocubyl 8-acetates (type B), viz 8-acetoxypentacyclo[5.3.0^2,5.0^3,9.0^4,8]decan-6-one 15, its ethylene acetal 16 and the parent acetate 20 has been carried out starting from the cyclopentadiene-benzoquinone adduct 7. Base induced homoketonization of 6, 16 and 20 leads regio- and stereospecifically to the thermodynamically favored half cage ketones 22,28 and 31, respectively. In contrast, the cage opening of the β-ketoacetates 5 and 15 is essentially directed by the β-ketone function. In the case of 5, regiospecific cleavage of the central C₄-C₅ bond is observed producing in a stereospecific manner diketone 25 in quantitative yield. Under similar conditions, acetate 15 gives a complex mixture of cage opened products arising from further fragmentation of the initially formed diketone 34. Deuterium labeling experiments reveal an anti-Bredt behavior of half cage ketones 28 and 31. The synthesis of a bridgehead acetate of type C has been accomplished by stereoselective reduction of ketone acetate 5 with LiAlH(t-OBu)₃ followed by mesylation. A mixture of epimers 36a and 36b (ratio 1:4) is obtained from which the predominant anti-epimer 36b could be isolated. An X-ray analysis established its structure. Base induced cage fission of 36b leads regiospecifically to tetracyclo[5.3.0.0^2,5.04,8]decenone 37. In contrast the syn-epimer 36a, under similar conditions, only affords the bridgehead alcohol 38.     

Enzymatic Kinetic Resolution of 5-Hydroxy-4-oxa-endo-tricyclo[5.2.1.0(2,6)]dec-8-en-3-ones: A Useful Approach to D-Ring Synthons for Strigol Analogues with Remarkable Stereoselectivity

Racemic 5-hydroxy-4-oxa-endo-tricyclo[5.2.1.0(2,6)]dec-8-en-3-one and its 2-methyl analogue were resolved employing a lipase-catalyzed acetylation reaction. The latter compound thus gave access to a homochiral D-ring synthon for strigolactones. The enzymatic acetylation reaction occurred with a remarkable inversion of configuration at C-5, through which it is possible to achieve a highly efficient asymmetric synthesis of 5-acetoxy-2(5H)-furanone.     

Chemistry of strained polycyclic compounds—V : The stereospecific cationic cage expansion reaction of 4-homocubane carbinols to 1,3-bishomocubane bridgehead alcohols

The cationic rearrangement of four homocubane bridgehead carbinols viz dimethyl 4-(1-bromopentacyclo[4.3.0.0^2,5.0^3,8.0^4,7]nonyl-9-one ethylene ketal) carbinol 2, diphenyl 4-(1-bromopentacyclo[4.3.0.0^2,5.0^3,8.0^4,7]nonyl-9-one ethylene ketal) carbinol 3, 4-(1-bromopentacyclo[4.3.0.0^2,5.0^3,8.0^4,7] nonyl-9-one ethylene ketal) carbinol 4 and 4-(1-bromopentacyclo[4.3.0.0^2,5.0^3,8.0^4,7]nonyl) carbinol 16, has been studied undervarious conditions.Exclusive migration of the C₄C₇ (or the equivalent C₃C₄ bond) in the homocubane skeleton was observed leading to 1,3-bishomocubane bridgehead alcohols. Relief of cage constraint governs the selective course of these cage expansions.     

Crystal and molecular structure of (3aR,8bS,5′R)3-[(2,5-dihydro-3-methyl-2-oxo-5-furanyl)oxymethylene]-3,3a,4,8b-tetrahydroindeno[1,2-b]furan-2-one

The stereogeometry and absolute configuration of the title compound has been proved by an X-ray diffraction analysis. Crystal data: monoclinic, C2,a=20.2528(4),b=6.7254(2),c=10.6748(2) Å, =94.699(3),Z=4. The crystal structure has been solved by vector search methods and refined toR ₁=0.053 for 2043 observed reflections.     

Structure and absolute configuration of 10-chloro-10-sulfinylcamphor,C10H13ClO2S

The structure of the title compound, C₁₀H₁₃ClO₂S, was determined by X-rays:M _r =232.72, monoclinic, space groupP2₁,a=6.4902(6),b=12.022(1),c=14.130(3) Å,=103.11(1)°,V _c =1073.7 ų,Z=4,D _x =1.44 Mg m^–3. MoK radiation (graphite crystal monochromator, =0.71069 Å),(MoK)=4.9 cm^–1,F(000)=342,T=293 K. Final conventionalR-factor=0.035 for 2221 observed reflections and 252 variables. The structure was solved usingDirdif. The absolute configuration of the structure is reported. The two independent molecules differ primarily in the orientation of the sulfine group with respect to the camphor moiety.On leave from the Department of Chemistry, University of Colorado, Boulder, Colorado 80309.     

Crystal and molecular structure of rac(1R,5S,6S,7R)-1-oxy-7-benzoyl-5-methyl-8-azabicyclo-[4.3.0]nonane-4,9-dione,C16H17NO4 (perhydroindole)

The structure of the title compound (perhydroindole) was determined by X-rays, using CuK radiation (graphite-crystal monochromator,=1.54184 Å): T=290 K., C₁₆H₁₇NO₄,M _r =287.31 monoclinic, space groupC2/c,a= 14.471(1),b=6.169(2),c=32.065(2) Å,=92.192(6)V _c =2860,6 ų,Z=8,D inx=1.338 Mg m^–3, (CuK)=7.54 cm^–1. Final conventionalR-factor=0.048, (R _w =0.072) for 2513 unique reflections and 258 variables. The structure was solved usingMultan. The six-membered ring of the molecule is in the chair configuration. The molecules are connected by hydrogen bonds.