Dipole moments and molecular conformations of some thioanhydrides

Electric dipole moments of methyl thiobenzoate (1.70 D), thiophthalic anhydride (3.92 D) and dibenzoyl sulphide (3.88 D) have been measured in benzene at 25° C. The predicted moments of these compounds were calculated and the results interpreted in terms of their conformations.     

Synthesis and study of mixed thioanhydrides of 1, 3-alkylenedithiophosphorous and O,O-dialkyldithiophosphoric acids

Conclusions The previously unknown mixed thioanhydrides of 1,3-alkylenedithiophosphorous and O,O-dialkyldi-thiophosphoric acids were obtained and some of their chemical properties were studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2060–2064, September, 1975.     

Photochemistry of thioanhydrides. Photofragmentation of cis-1,2-dihydrophthalic thioanhydrides

$\text{Cis}$-1,2-Dihydrophthalic thioanhydride ($\text{2}$) and some substituted derivatives were prepared and found to undergo irradiation induced, high quantum-yields CO+COS extrusion from a siglet and a (high) triplet excited state.     

Synthesis of ring modified prostaglandins

The total syntheses of the ring modified prostaglandins 8–12, 16, 18, 20, and 22 are described.     

Synthesis of the ravidomycin ring system

Synthesis of the tetracyclic aromatic ring system of the ravidomycin family of anti-tumor agents is reported. The synthesis is a sequential Meerwein and Diels-Alder route with the crucial regiochemistry of the Diels-Alder reaction controlled with a chlorine atom.     

Synthesis and characterization of ring polybutadienes

It has been shown that butadiene initiated with potassium naphthalene in the mixture THF-n-hexane polymerizes conveniently rapidly. The active center is sufficiently stable below 0°C to produce narrow molecular weight linear polybutadiene. The two-ended living polymer has also served to prepare ring polybutadienes. The analysis of the ring polymers by a high-resolution set of SEC columns proved superior to the conventional method for the determination of the linear content in rings and in synthetic mixtures of rings and linear polymers. Dilute solution characterization of the linear and ring polymers shows that g_r′ = [η]/_r[η]_l is less than 0.66 in a good solvent.     

Synthesis of large ring crown ethers

The synthesis of large ring crown compounds with the general structure 3n-crown-n where n is 9 to 20 is reported.     

Synthesis of the guanacastepene A-B hydrazulene ring system through photochemical ring transposition

The A-B hydrazulene ring system of the guanacastepenes has been synthesised using a photochemical ring transposition of a 6-6 bicycle.     

Synthesis of the ABCD ring of gambierol

A fully functionalized ABCD ring moiety of gambierol, a marine polycyclic ether toxin, was synthesized by the use of the oxiranyl anion strategy and reductive cycloetherification of a beta,delta-dihydroxy ketone.     

Synthesis of the 13,14-diazasteroid ring system

l-Vinyl-6-methoxy-3,4-dihydronaphthalene (1) reacted with azo dienophiles to form cyclo-adducts II, III, IV, and V. The reaction of adduct II with bromine resulted in the aromatization of the B ring to form the cycloadduct VIII.     

Synthesis of the celogentin C right-hand ring

[reaction: see text] Synthesis of the cyclic tetrapeptide comprising the right-hand ring of celogentin C, a potent inhibitor of tubulin polymerization, has been accomplished. A mild oxidative coupling reaction permitted construction of the indole-imidazole linkage via a convergent union of two fully functionalized dipeptides. A high-yielding macrolactamization and subsequent deprotection of the N-terminus furnished the target compound.     

Synthesis and ring expansions of functionalized spirocyclobutanones

The first condensations between bis(trimethylsilyloxy)cyclobutene derivatives and functionalized orthoesters are reported. The resulting adducts are readily converted into spirocycloethers, which undergo a variety of -CH2- and -O- insertions with excellent regioselectivity.     

Synthesis of cholaphanes by ring closing metathesis

The synthesis of cholaphanes by ring closing metathesis (RCM) of 3α,7α,12α,24-tetraol allyl derivatives, obtained from cholic acid, was attempted. The reactions of tetraol 3,24-diallyl ether or 3,24-diacrylate were not satisfactory. However, diallyl derivatives of disteroidal 3,3′- or 24,24′-ortho-phthalates reacted smoothly affording cyclic dimers in good yields. In all the reactions studied, the E isomers of the macrocycles were obtained in excess.     

Synthesis and ring contraction reactions of polyazamacrolides

The synthesis of three analogues of the single most abundant component of a ladybird beetle (Epilachna borealis) defensive secretion, the trimeric 42-membered polyazamacrolide PAML 681, is described. Construction of the nonnatural macrocyclic trimers began with the preparation of the corresponding monomeric segments, followed by their oligomerization and a final macrolactonization step of the activated linear trimeric hydroxy acid. The relative rates of the O-to-N acyl migrations that are characteristic of PAML 681 itself, as well as of the synthetic analogues, were investigated. These studies showed that changes in the substitution pattern adjacent to the nucleophilic nitrogen atom, along with changes in the size of the oxaazacyclic intermediates, have substantial effects on the polyazamacrolide rearrangement rates.     

Synthesis of azaphenanthridines via anionic ring closure

A new and convergent synthesis of azaphenanthridines via an anionic ring closure is reported. Ortho-lithiation/in situ borylation of cyanopyridines produces the corresponding cyanopyridylboronic esters, which undergo a Suzuki-Miyaura cross-coupling to give the key intermediates. Addition of lithium morpholide produces the azaphenanthridines.     

Synthesis of the NO ring model of gymnocin-B

A synthetic route to the NO ring model of gymnocin-B, a cytotoxic marine polycyclic ether with the largest contiguous rings, has been achieved. The synthesis features construction of the seven-membered O ring with 1,3-dimethyl substituents flanking the ether oxygen by ring-closing metathesis.     

Synthesis of the hydroazulene ring system of guanacastepene

[reaction: see text] A 12-step synthesis of 26, the functionalized hydroazulenone ring of guanacastepene (1), has been completed using the EtAlCl(2)-initiated cyclization of gamma,delta-unsaturated ketone 13 to construct 2,2,3-trisubstituted cyclopentanone 14, the palladium-catalyzed coupling of vinylmagnesium bromide with enol triflate 17 to prepare triene 21, and olefin metathesis of triene 21 to form the key hydroazulene 20.     

Synthesis of eight-membered ring compounds using enyne metathesis

[reaction: see text] A novel procedure for synthesizing eight-membered ring compounds was developed using ruthenium-catalyzed enyne metathesis. When a CH2Cl2 solution of enyne connected with catechol, o-amino phenol, or o-phenylenediamine was stirred in the presence of benzylidene ruthenium carbene complex (10 mol %) at room temperature overnight, an eight-membered ring compound was obtained in high yield. In a similar manner, monocyclic 1,4-diaza- or 1-oxa-4-azacyclooctene derivative was obtained in high yield.     

Synthesis of indoles with a polyfluorinated benzene ring

A two-step sequence consisting of a Sonogashira coupling of polyfluorinated 2-iodoanilines with terminal alkynes, followed by a KOH promoted cyclization of the 2-alkynylanilines thus formed, has been developed as a one-pot synthesis of 2-R-indoles (R=n-Bu, Ph, CH₂OTHP→CH₂OH, C(CH₃)₂OH→H) containing a polyfluorinated benzene moiety.     

Synthesis of spirocyclic butenolides by ring closing metathesis

Spirocyclic butenolides were efficiently prepared by a ring closing metathesis strategy.