Studies in sesquiterpenes-XL. Isolongifolene (part 1): Structure

Isolongifolene, C15H24 an artefact from an acid-catalysed rearrangement of longifolene, is shown to be II.

Structure of abnormal products isolated from the isomerization of 7-methoxychromano3,4-disoxazole - A novel synthesis of one of the products

A one-step synthesis of (IIb), an isomerization product of 7-methoxychromano3,4-disoxazole, from (III) is reported.

Synthesis of Unnatural Selenocystines and beta-Aminodiselenides via Regioselective Ring-Opening of Sulfamidates Using a Sequential, One-Pot, Multistep Strategy

A variety of N-alkyl-beta-aminodiselenides have been synthesized in high yield from sulfamidates under mild reaction conditions using potassium selenocyanate and benzyltriethylammonium tetrathiomolybdate ([BnNEt3](2)MoS4) in a sequential, one-pot, multistep reaction. The tolerance of multifarious protecting groups under the reaction conditions is discussed. The methodology was successfully extended to the synthesis of selenocystine,3,3'-dialkylselenocystine, and 3,3'-diphenylisoselenocystine and their direct incorporation into peptides.

Reactions of tetrahalogeno-1,2-benzoquinones. Part III. Reaction of tetrachloro-1,2-benzoquinone with tetralones and naphthols: Pathway to the condensates

With a view to understanding the mechanism of the formation of 6-methoxy-2,2-(tetrachloro--phenylenedioxy)-naphthalen-1 (2H)-one (IIIa) in the reaction of 6-methoxy-1-tetralone (Ia) with tetrachloro-1,2-benzoquinone (II), the reaction of (II) with various tetralones and naphthols has been studied. Reaction with either α-tetralone or α-naphthol gives 2,2-(tetrachloro-o-phenylenedioxy)naphthalen-1 (2H)-one (IIIb), whereas reaction with either β-tetralone or β-naphthol gives a mixture of (IIIb) and ,1-(tetrachloro-o-phenylenedioxy)-naphthalen-2 (1H)-one (IX), with the former predominating. Further, reactions of (II) with 7-methoxy-3,4-dihydrophenanthren- 1 (2H)-one and m-methoxyphenol gave respectively 7-methoxy- ,2-(tetrachloro-o- phenylenedioxy)phenanthren-1 (2H)-one (VII) and 3-methoxy-6,6-(tetrachloro-o- phenylenedioxy)cyclohexa-2,4-dien-1-one (VIII). Structures of all these compounds have been proved on the basis of i.r. and n.m.r. data. The pathway to the formation of the condensates (III) is discussed.

Reaction of carbon disulfide with azide ion

Carbon disulfide reacts with azide ion to form the 1,2,3,4-thiatriazolinethionate ion and not the acyclic azido dithiocarbonate ion as previously reported. A series of salts of thiatriazoline have been prepared and none shows evidence for the presence of the azido group. Esters of thiatriazolinethione prepared by the reaction of the sodium salt with alkyl or acyl halides have been found to be either 5-(substituted) mercapto-1,2,3,4-thiatriazoles or 4-substituted 1,2,3,4-thiatriazoline-5-thiones. These structures have been assigned on the basis of degradative and spectroscopic evidence. The chemistry of the so-called azidodithiocarbonates has been reinterpreted in terms of the thiatriazole structure.

Studies in sesquiterpenes-XX. Acetoxymethylation of longifolene

Longifolene in Prins reaction with formaldehyde yielded the expected ω-acetoxymethyl longifolene, which was transformed into a number of interesting derivatives. Configuration of the Prins product has been arrived at by NMR measurements. The UV absorption of these derivatives show a considerable bathochromic shift with respect to those in the camphene series and this could be attributed to the slight twisting of the ethylenic linkage in longifolene and its derivatives.

Studies in sesquiterpenes-XIX. Action of perbenzoic acid on longifolene

Oxidation of longifolene, a mono-olefinic sesquiterpene, with a chloroform solution of perbenzoic acid proceeded to almost two mole consumption of the peracid to furnish a number of products, important ones being an α-ketol, a norketone (longicamphenilone) and the corresponding C14-alcohols. Under certain conditions it has been possible to arrest the reaction at one mole consumption and to isolate longifolene-α-epoxide, which is the major product; some amounts of epimeric longifolaldehydes and longicamphenilone were also formed. Further action of perbenzoic acid on longifolene oxide and longifolaldehydes has been investigated and the results used to interpret the mechanism of abnormal peracid oxidation of longifolene.

Conversion of an equilenane to the estrane: Synthesis of dl-3-methoxy-17β-carboxy-1,3,5(10)-estratriene

dl-3-Methoxy-11-oxo-17β-carboxy-1,3,5(10),6,8-estrapentaene has been converted to dl-3-methoxy-17β-carboxy-1,3,5(10)-estratriene in fairly good yield.

A new synthesis of dl-3-methoxy-17β-carboxy-1,3,5(10),6,8-estrapentaene

3-Methyl-4-carboxy-2-(2′-methoxy-6′-naphthyl)cyclopenten-3-acetic acid, prepared from trans methyl 2-methyl-3-carbomethoxycyclopentanon-2-acetate and 2-methoxy-6-lithionaphthalene, on ring closure and catalytic hydrogenation gave dl-3-methoxy-17β-carboxy-1,3,5(10),6,8-estrapentaene.

Synthetic investigations in the sesamin group - Part I. Synthesis of samin, a degradation product of sesamolin

Ethylα-bromovinylacetate (VII) was condensed with the sodio derivative of ethyl piperonoylacetate (VIII) to give diethylα-vinyl-α′-piperonoylsuccinate (IX). The latter on reduction with lithium aluminium hydride furnished the triol (X), which underwent smooth cyclisation with 1% ethanolic hydrogen chloride to 2-(3′, -methylenedioxyphenyl)-hydroxymethyl-4-vinyltetrahydrofuran (XIa). The structure of XIa was established by Oppenauer oxidation to an aldehyde. Ozonolysis of XIa afforded samin (I).

Studies in the Sandalwood Oil Series. III. Chain Effect on Terpene Transformations

The carboxyl chain of some molecules has been found to be responsible for causing rearrangements and controlling their course. This chain effect, which operates during reactions involving carbonium ions, is illustrated with examples from Sandalwood oil chemistry.

Mechanism of the addition of alcohols to substituted phenylisothiocyanates : Electrical effects of the substituents on the reaction

The addition reaction of alcohols to substituted phenylisothiocyanates is found to be a second-order reaction. The reaction is catalysed by triethylamine. First-order rate constants of the addition reaction have been determined in excess of ethanol, for a number of substituted phenylisothiocyanates and the rate data give a satisfactory linear correlation with Hammett σ constants of groups. While the energies of activation vary randomly with substitution, the entropies of activation bear a linear relationship to the energies of activation. Infra-red spectra indicate that the thiourethanes which are the products of the addition reaction exist in the thioamide form. The most prominent resonance form which can satisfactorily explain both the kinetic and infrared data, has been suggested.

The C=S stretching frequency and the “-N-C=S bands” in the infrared

A correlation of the infrared spectra of thiocarbonyl derivatives based on the literature data has been carried out. Assignments have also been made in some new systems. Since simple alkyl thioketones are unstable, we have prepared thiofenchone in order to obtain a reference C=S stretching frequency. The C=S stretching frequency in thiofenchone has been found around 1180 cm−1 which is in fair agreement with the value calculated for thioformaldehyde. In the case of the thiocarbonyl derivatives where the C=S group is linked to elements other than nitrogen, the stretching frequency is generally found in the region 1025–1225 cm−1. Strong vibrational coupling is operative in the case of the nitrogen containing thiocarbonyl derivatives and three bands seem to consistently appear in the regions 1395–1570 cm−1, 1260–1420 cm−1, 940–1140 cm−1 due to the mixed vibrations. These bands, which may be tentatively designated as the “-N-C=S I, II and III bands”, could be useful in qualitative analysis.

Infrared spectra of substituted benzoyl chlorides and benzoyl bromides. Explanation of the anomalous carbonyl band-splittings

Infrared spectra of substituted benzoyl chlorides and benzoyl bromides have been studied. The extent of splitting of the carbonyl band in benzoyl chlorides varies with substitution. While benzoyl bromide shows the carbonyl band as a single peak, para-nitrobenzoyl bromide shows a doublet. The results are interpreted in terms of intramolecular vibration effects (Fermi resonance). The intense band in the 860–880 cm−1 region in benzoyl chloride and benzoyl bromide has been assigned to the Ph-C stretching vibration.