Tetracyclines Communication 33. Synthesis of 8-chloro-5-methoxy-3,10-dioxo-1,2,3,4,4a,9,9a,10-octahydroanthracene [5-chloro-1,3,4,4a,9a,10-hexahydro-8-methoxy-2,9-anthracenedione]

Summary 8-Chloro-5-methoxy-3,10-dioxo-1,2,3,4,4a,9,9a,10-octahydroanthracene (Ib) was synthesized; this can serve as an intermediary in the preparation of the tetracyclic analog (IIb) of aureomycin,Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 806–810, May, 1965 Original article submitted April 22, 1963For preceding communication see [1],The authors thank L. B. Senyavina for infrared spectrum measurements.     

Synthesis of 1-Bromosubstituted Analogs of cis-Deltamethrinic and cis-Permethrinic Acids

In the synthesis of 1-bromosubstituted analogs of cis-deltamethrinic and cis-permethrinic acids, main components of pyrethroids, the key stage is an intramolecular 1,4-O,C-acyl transfer in reactions of 1-acyloxymethyl-2,2-dibromocyclopropanes with methyllithium.     

Synthesis and some chemical transformations of 3-ferrocenyl-3-phenylcyclopropene

Crystalline 3-ferrocenyl-3-phenylcyclopropene was obtained by dehydrobromination of 2-bromo-l-ferrocenyl-l-phenylcyclopropane with potassiumtert-butoxide in dimethyl sulfoxide. The compound synthesized undergoes catalytic hydrogenation to l-ferrocenyl-I-phenylcyclopropane, reacts with 1,3-diphenylisobenzofuran to give the expected product of stereospecific [4+2[-cycloaddition and 3-ferrocenylindene, and also undegoes opening of the small ring on treatment with superacids to give 3-ferrocenylindene as the major product. The data of single crystal X-ray diffraction analysis of 1-ferrocenyl-l-phenylcyclopropane and the diene adduct of 3-ferrocenyl-3-phenylcyclopropene with 1,3-diphenylisobenzofuran are given.     

Tetracyclines Communication 34. Synthesis of the 6-demethyltetracycline analog 2-decarbamoyl-4-dedimethylamino-6,10,12-tridehydroxy-6-demethyl-11a,12-dihydrotetracycline

Summary A tetracyclic analog of 6-demethyltetracycline-2-decarbamoyl-4-dedimethylamino-6,10,12-tridehydroxy-6-demethyl-11a,12-dihydrotetracycline-was synthesized.For preliminary communication see [1].The authors thank L. B. Senyavina for the measurement of infrared spectra.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1039–1044, June, 1965     

Functionalized α-bromocyclopropylmagnesium bromides: Generation and some reactions

Functional derivatives of gem-dibromocyclopropanes (ethers and esters of gemdibromocyclopropylmethanol, 2,2-dibromocyclopropanecarboxylic acids and their esters) undergo partial hydrodebromination at the treatment with isopropyl magnesium bromide (3–6 mol-equiv) in THF and then in methanol at ?60°C affording the corresponding monobromides in 64–95% yields. The addition of nonsolvated magnesium bromide to the reaction mixture results in the considerable reduction of the amount of the Grignard reagent (from 6 to 3 mol-equiv). This allows achieving the partial hydrodebromination of 2,2-dibromocyclopropanecarboxylic acids.     

Effective and Selective Mild Catalytic Hydrodehalogenation of Halocyclopropanes: Preparative Capabilities and Mechanistic Aspects

This review surveys both data obtained by the authors and published data on the partial or full hydrodehalogenation of di- and polyhalocyclopropanes (chlorides and bromides) with Grignard reagents catalyzed by titanium or zirconium compounds. The factors affecting the efficiency and selectivity of the hydrodebromination of bromocyclopropanes are considered: the nature of Grignard reagents (including isotopically labeled reagents), their transformations and effects in catalyzed and uncatalyzed reactions, the participation of solvents, catalytic and stoichiometric amounts of the catalyst, etc. A scheme is proposed in which the key steps of the mechanism of hydrodebromination of bromocyclopropanes includes three blocks of reactions: (a) the generation of a catalytically active Ti(II) species; (b) the hydrodehalogenation of bromocyclopropanes involving electron transfer from a low-valent catalyst species, formation of the cyclopropyl radical, and stabilization of this radical as a result of hydrogen atom transfer from the solvent molecule; and (c) transformations of previously formed radical species, such as dimerization and disproportionation (for example, of radical species generated from Grignard reagents or ether molecules) or the linking of alkyl radicals to radical species produced from solvent molecules.     

Stereocontrol in ene-dimerisation and trimerisation of 1-trimethylsilyl-3-phenylcyclopropene

1-Trimethylsilyl-3-phenylcyclopropene undergoes a highly stereocontrolled ene-reaction to give a dimer and further reaction leads to one or more trimers derived through two ene-reactions.