Perfluoroalkylsulfonyl fluoride-mediated abnormal Beckmann rearrangement of steroid 17-oximes with acid-labile groups

A perfluoroalkylsulfonyl fluoride-mediated abnormal Beckmann rearrangement is reported which transforms steroid 17-oximes to the corresponding alkene nitriles regioselectively in good yields. This reaction is rapid (completes in 25 min), mild (proceeds at room temperature) and, most importantly, tolerates various acid-labile functional groups, such as methoxymethyl (MOM), ketal, and methyl enol ether, providing access to molecules that would be difficult to synthesize using existing methods.     

Study on the preparation of heteroaryl substituted enamines. A simple synthesis of heteroaryl substituted acetaldoximes from enamines

A comparative study of the reactivity of methyl groups towards N, N-dimethylformamide dimethyl acetal and tert-butoxybis(dimethylamino)methane was carried out on methyl substituted six-membered nitrogen containing heterocycles 1 to give enamines 2 , which were easily transformed to oximes by treating with hydroxylamine hydrochloride in methanol. Most of them were isolated as (E, Z)-oximes of heteroarylacetaldehyde ( 11 ), but 5-(1,2,4-triazinyl) substituted derivatives as (E, Z)-oximes of 2,5-dihydro-1,2,4-triazin-(Z)-5-ylideneacetaldehyde ( 11t, 11u , and 12 ). Oximes were finally transformed to the corresponding acetonitriles 16 and 3-(dimethylamino)acrylonitriles 17 .     

Reaction of 5-Substituted 2-(3-Chloropropanoylamino)benzophenone syn- and anti-Oximes with Sodium Hydroxide

Treatment of syn-oximes of 5-substituted 2-(3-chloropropanoylamino)benzophenones with equimolar amount of sodium hydroxide results in formation of syn-oximes of 5-substituted 2-propenoylamino-benzophenones. The corresponding anti isomers under the same conditions give a mixture of anti-oximes of 5-substituted 2-(propenoylamino)benzophenones and 18-membered 11,22-disubstituted 7,8,18,19-tetrahydrodibenzo[d,m][1,10,2,6,11,15]dioxatetraazacyclooctadecine-6,17(5H,16H)-diones.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 969–977.Original Russian Text Copyright © 2005 by Andronati, Simonov, Pavlovskii, Kulikov, Gdanec, Mazepa.     

Synthesis and 5α-reductase inhibitory activity of C₂₁ steroids having 1,4-diene or 4,6-diene 20-ones and 4-azasteroid 20-oximes

The synthesis and evaluation of 5α-reductase inhibitory activity of some 4-azasteroid-20-ones and 20-oximes and 3β-hydroxy-, 3β-acetoxy-, or epoxy-substituted C?? steroidal 20-ones and 20-oximes having double bonds in the A and/or B ring are described. Inhibitory activity of synthesized compounds was assessed using 5α-reductase enzyme and [1,2,6,7-3H]testosterone as substrate. All synthesized compounds were less active than finasteride (IC??: 1.2 nM). Three 4-azasteroid-2-oximes (compounds 4, 6 and 8) showed good inhibitory activity (IC??: 26, 10 and 11 nM) and were more active than corresponding 4-azasteroid 20-ones (compounds 3, 5 and 7). 3β-Hydroxy-, 3β-acetoxy- and 1α,2α-, 5α,6α- or 6α,7α-epoxysteroid-20-one and -20-oxime derivatives having double bonds in the A and/or B ring showed no inhibition of 5α-reductase enzyme.     

Stereochemical effects in the nitrosation of some α,β-unsaturated ketoximes. Formation of 1-hydroxypyrazole 2-oxides and 4-oximino-4,5-dihydroisoxazoles

Several α,β-unsaturated ketoximes R¹CH=CHC(=NOH)R² were nitrosated using butyl nitrite in aqueous ethanol in the presence of copper(II) sulfate and pyridine. The product distribution varied depending on whether the oxime hydroxyl group was syn or anti with respect to the carbon?carbon double bond. The anti-oximes gave the copper complexes of 1-hydroxypyrazole 2-oxides in high yields. The isomeric syn-oximes gave lower yields of the pyrazole complexes along with 4-oximino-4,5-dihydroisoxazole derivatives. For the syn-oximes where R¹ is phenyl and R² is either methyl or ethyl, conversion of the oximes to the parent ketones was also observed. The results may be explained by processes involving N-nitrosonitrone intermediates.     

Mass spectra of 1-(2′-hydroxy-5′-alkylphenyl)-1-alkanone (E)-oximes

The mass spectra of 1-(2′-hydroxy-5′-alkylphenyl)-1-ethanone (E)-oximes 1–6 and 1-(2′-hydroxy-5′-methylphenyl)-1-alkanone (E)-oximes 7–12 are given and the major fragmentation pathways discussed. The simultaneous loss of water and alkyl moieties from the molecular ion indicates that a skeletal rearrangement take place and a cycloheptatrienyloheterocyclic system is formed. The McLafferty rearrangement, γ-fission in the side aliphatic chain and oxygen expulsion are discussed with evidence being drawn from accurate mass measurements, metastable ions and comparison with mass spectral data of related compounds.     

beta-Silylcarbenes from isolable diazosilanes.

Manganese dioxide oxidation of the hydrazone derivative of tert-butyldimethylsilyl acetophenone gave 2-tert-butyldimethylsilyl-1-phenyldiazoethane (17) an isolable diazocompound. Thermal and Rh(II)-catalyzed decomposition of diazosilane 17 in cyclohexane led to 1-tert-butyldimethylsilyl-1-phenylethylene (19) as the major product. The formation of alkene 19 presumably involves (tert-butyldimethylsilyl)methylphenylcarbene (21), which undergoes preferential 1,2-silyl migration as opposed to 1,2-hydrogen migration. Thermal decomposition of 17 in cyclohexane under oxygen gave substantial amounts of tert-butyldimethylsilyl acetophenone, presumably by reaction of the intermediate carbene with oxygen. Thermal decomposition of 17 in methanol led to alkene 19 and 2-tert-butyldimethylsilyl-1-methoxy-1-phenylethane (22) as major products, along with a significant amount of trans-1-tert-butyldimethylsilyl-2-phenylethylene (20). Kinetic studies indicate that these products are not derived from acid-catalyzed decomposition of the diazocompound 17. Formation of the methyl ether product 22 suggests the involvement of a beta-silyl carbocation intermediate, and solvent isotope effect studies indicate that this cation is at least partially derived from protonation of diazocompound 17 by neutral methanol. Photochemical decomposition of 17 in methanol produced the alkene 19 (97%) along with a small amount (2.4%) of the methyl ether 22. Capture of a photochemically generated carbene 21 by methanol is the proposed origin of this minor product. Geometry optimization of trimethylsilylmethylphenylcarbene (8) and carbene 21 at the HF/6-31G computational level led to a conformation consistent with a hyperconjugative interaction between the vacant p-orbital of these carbenes and the adjacent C-Si bond. Carbenes 8 and 21 are not energy minima at the B3LYP/6-31G level, where they rearrange to alkenes without barrier via silyl migration. These theoretical findings contrast with the proposed trapping of carbene 21 by methanol and oxygen.     

A formal total synthesis of the salicylihalamides

The synthesis of the macrolactone 23 is described. The synthesis features a diastereoselective hydroboration of the chiral alkene 17 followed by a Suzuki cross-coupling reaction with the benzoate 5. The resulting seco acid 21 was converted to the macrolactone 23 by a Mitsunobu lactonization using immobilized triphenylphosphine. The stereogenic centers in the alkene 17 were established by a Noyori reduction of the beta-keto ester 8 and an Evans aldol reaction. The synthesis illustrates the conversion of a syn aldol product to the corresponding anti product by inversion of the methyl-bearing center.     

Synthesis of cyclopent[bindoles by formal [3+2]-addition of indolylmethyl cations to alkenes

Treatment of indole-2- or 3-methanols with tin(IV) chloride as Lewis acid in the presence of styrenes results informal [3+2]-addition of the indole stabilised cation to the alkene to give cyclopent[b]indoles with a high degree of stereoselectivity; use of methylcyclohexene as the alkene component gave the cis-fused cyclopent[b]indole 17, which was independently synthesised in enantiomerically pure form from the diketone 18.     

Reactions of (4E)-3-Arylamino-4-(hydroxyimino)naphthalen-1(4H)-ones and (4E)-2-[Arylamino(alkylamino)]-4-(hydroxyimino)naphthalen-1(4H)-ones with 2,2-Dihydroxyindane-1,3-dione

Russian Journal of Organic Chemistry - The reactions of 3-arylamino-1,4-naphthoquinone-4-oximes with 2,2-dihydroxyindane-1,3-dione proceed without involving the oxime group and lead to...     

Acylating and arylsulfonylating ability of O-derivatives of isatin 3-oximes

O-Acyl and O-arylsulfonyl derivatives of isatin 3-oximes have been synthesized and their interaction with alcohols and amines has been investigated. It was established that none of the esters of 1-substituted isatin 3-oximes reacted with the indicated nucleophiles. 1-Unsubstituted O-aryl and O-arylsulfonyl derivatives react with amines as acylating agents even at room temperature, but O-acetyl derivatives only on heating. Acylamides or arylsulfamides respectively are formed in this way. O-Acyl derivatives do not react with alcohols at room temperature. Only O-benzoyl derivatives form ethyl benzoate on heating in ethanol. A comparative analysis of mass spectrometric data on the processes of acylation and arylsulfonylation is given.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 113–119, January, 2005.     

A versatile synthetic route to 11H-indolo[3,2-c]isoquinolines

A wide variety of indoloisoquinoline derivatives are prepared from the acid-catalyzed cyclization of 3-amido-2-phenylindoles, which in turn were obtained from the Beckmann rearrangement of 2-phenylindole-3-oximes.     

Functionalization of Testosterone at Position 7α and Synthesis of 7α-(3-Methoxypropyl)-4-androsten-17β-ol-3-one

An efficient transformation of the terminal alkene function of 7α-allyltestosterone is reported along with the stereospecific synthesis of 7α-(3-methoxypropyl)-4-androsten-17β-ol-3-one.     

Synthesis of 4-Aminodihydroquinopimaric Acid Derivatives

Russian Journal of Organic Chemistry - The reduction of 4-oximes derived from 1β-hydroxy-, 1β,13-epoxy-, and 1,1-(ethylenedioxy)dihy­dro­quinopimaric acid methyl esters, as well...     

A hetero-Diels-Alder approach to functionalized 1H-tetrazoles: synthesis of tetrazolyl-1,2-oxazines, -oximes and 5-(1-aminoalkyl)-1H-tetrazoles

This work describes the first and unprecedented examples of inverse electron demand Diels-Alder reactions of 5-(1-nitrosovinyl)-1-phenyl-1H-tetrazole, generated in situ from the corresponding bromooxime, with electron rich alkenes and heterocycles, providing in good overall yields tetrazolyl-1,2-oxazines and -oximes. Upon subsequent reduction these allowed the access to 5-(1-aminoalkyl)-1H-tetrazoles, paving the way for a new entry into this important class of compounds, bioisosteres of α-amino acids.     

Nonchelated d0 zirconium-alkoxide-alkene complexes

The reaction of Cp'2Zr(O(t)Bu)Me (Cp' = C5H4Me) and [Ph3C][B(C6F5)4] yields the base-free complex [Cp'2Zr(O(t)Bu)][B(C6F5)4] (6), which exists as Cp'2Zr(O(t)Bu)(ClR)+ halocarbon adducts in CD2Cl2 or C6D5Cl solution. Addition of alkenes to 6 in CD2Cl2 solution at low temperature gives equilibrium mixtures of Cp'2Zr(O(t)Bu)(alkene)+ (12a-l), 6, and free alkene. The NMR data for 12a-l are consistent with unsymmetrical alkene bonding and polarization of the alkene C=C bond with positive charge buildup at C(int) and negative charge buildup at C(term). These features arise due to the lack of d-pi* back-bonding. Equilibrium constants for alkene coordination to 6 in CD2Cl2 at -89 degrees C, K(eq) = [12][6](-1)[alkene](-1), vary in the order: vinylferrocene (4800 M(-1)) > ethylene (7.0) approximately alpha-olefins > cis-2-butene (2.2) > trans-2-butene (<0.1). Alkene coordination is inhibited by sterically bulky substituents on the alkene but is greatly enhanced by electron-donating groups and the beta-Si effect. Compounds 12a-l undergo two dynamic processes: reversible alkene decomplexation via associative substitution of a CD2Cl2 molecule, and rapid rotation of the alkene around the metal-(alkene centroid) axis.     

Carbasaccharides via Ring-Closing Alkene Metathesis. A Synthesis of (+)-Valienamine from D-Glucose

(+)-Valienamine ( 16 ) was prepared in seven steps and in an overall yield of 17% from commercially available 2,3,4,6-tetra-O-benzyl-D -glucopyranose. Stereoselective addition of vinylmagnesium bromide to the 1,3,4,5-tetra-O-benzyl-6,7-dideoxy-L -xylo-hept-6-en-2-ulose ( 2 ) gave diene 3 (86%). Ring-closing alkene metathesis of 3 in the presence of 0.15 equiv. of Grubb's catalyst 1 gave the cyclohexene 4 (58%), that was converted into (+)-valienamine ( 16 ) in three steps and in 47% yield. Similarly, ring-closing alkene metathesis of the D -mannose-derived diene 20 gave the cyclohexene 21 (89%).     

New methodology for the synthesis of thiobarbiturates mediated by manganese(III) acetate

A three step synthesis of various thiobarbiturate derivatives 17-24 was established. The first step is mediated by Mn(OAc)?, in order to generate a carbon-carbon bond between a terminal alkene and malonate. Derivatives 1-8 were obtained in moderate to good yields under mild conditions. This key step allows synthesis of a wide variety of lipophilic thiobarbiturates, which could be tested for their anticonvulsive or anesthesic potential.     

Copper-catalyzed cyclization of Z-oximes into 3-methyl-1,2-benzisoxazoles

A practical and effective room temperature copper-catalyzed cyclization of Z-oximes is developed. 3-Methyl-1,2-benzisoxazoles are obtained in 58-79% yields. Also, the Z-selective synthesis of o-bromo acetophenone oximes is presented for the first time.     

Innovative reactions mediated by zirconocene

Radical reactions mediated by Schwartz reagent and zirconocene(alkene) complex are firstly described. Schwartz reagent is a promising alternative to tributyltin hydride and the first transition metal hydrido complex used as a radical mediator in organic synthesis. A zirconocene(alkene) complex effects single electron transfer to alkyl halide to generate the corresponding alkyl radical. Secondly, serendipitous allylic C-H bond activation of the coordinating alkene of zirconocene(alkene) complex and its application to organic synthesis are summarized. By utilizing equilibrium between zirconocene(alkene) and zirconocene 2-alkenyl hydride, reaction of acid chloride with zirconocene(alkene) provides the corresponding homoallylic alcohol by sequential attacks of the hydride and 2-alkenyl moieties. A set of hydride and 2-alkenyl attacks on 1,4-diketone yields 6-heptene-1,4-diol derivative in high yield with high stereoselectivity. Selective capture of the hydride with diisopropyl ketone gives zirconocene 2-alkenyl alkoxide, which is a useful reagent for stereoselective allylation of aldehyde and imine. alpha-Halo carbonyl compounds undergo radical allylation with the zirconocene 2-alkenyl alkoxide which serves as a substitute for allyltin.