Photochemical Rearrangement of a Steroidal α, β-Epoxylactam. Photochemical reactions,XII [1]

The UV. irradiation of 17β-hydroxy-4α, 5α-epoxy-2-azaandrostan-3-one ( 1 ) yields 17β-hydroxy-2-aza-10 (5 → 4-abeo)-4ζ (H)-androsta-3,5-dione ( 3 ).     

Photochemical Rearrangement of a Steroidal α,β-Epoxylactone. Photochemical reactions,XI [1]

The UV. irradiation of 17β-acetoxy-4α, 5α-epoxy-2-oxaandrostan-3-one ( 7 ) yields 17β-acetoxy-2-oxa-10(5 → 4)abeo-4ζ (H)-androsta-3,5-dione ( 11 ). A non-photochemical synthesis of 11 , proceeding in lower yield, is also described.     

Photochemical reactions. 141st communication. Photochemistry of α,β-unsaturated δ,ϵ-epoxyketones of the ionone series

On n,π*- as well as on π,π*-excitation, the 4,5-epoxy-α-ionones (E)- 1 , (E)- 2 , and (E)- 3 undergo (E)/(Z)-isomerization and subsequent γ-H-abstraction leading to the corresponding 4-hydroxy-β-ionones (E/Z)- 9 , (E/Z)- 13 , and (E/Z)- 17 as primary photoproducts. On photolysis of (E)- 3 , as an additional primary photoproduct, the β,γ-unsaturated σ,?-epoxy ketone 18 was obtained. The other isolated compounds, namely the 2H-pyrans 10A + B and 14A + B as well as the retro γ-ionones 11 and 15A + B , represent known types of products, which are derived from the 4-hydroxy-β-ionones (E/Z)- 9 and (E/Z)- 13 , respectively.     

Synthesis of α,β-unsaturated oxathiolanes

The formation of α,β-unsaturated oxathiolanes 2 from α,β-unsaturated carbonyl derivatives was achieved selectively and in high yields using the heterogeneous catalyst APSG·HCl.     

A Norrish Type I cleavage in the photolysis of a steroidal α,β-unsaturated δ-lactone. Photochemical Reactions. XIV [1]

The UV. irradiation of 17 β-acetoxy-4-oxa-5 α-androst-1-en-3-one (1) yields A,B-diseco-steroids originating from a Norrish I process of the lactone function.     

Structure and reactivity of α,β-unsaturated ethers. XIII. Cationic copolymerization and acid-catalyzed hydrolysis of 1,2-dialkoxyethylenes

The cationic copolymerizations of geometrical isomers of 1,2-dimethoxy- and 1,2-diethoxyethylenes with vinyl isobutyl ether as a reference monomer have been carried out in methylene chloride at ?70° using boron trifluoride etherate as catalyst. The kinetics of the acid-catalyzed hydrolysis of these ethers has also been investigated in 80% aqueous dioxane, in order to compare the results with the polymerizabilities. It has been found that the cis ethers are ca. four times as reactive as their trans isomers in both reactions. On the other hand, it has been proved that a β-alkoxyl substitution reduces the hydrolysis reactivity of vinyl alkyl ethers by a factor of ca. 10^?3 while it even enchances the cationic polymerizability. These contrasting results are interpretable from the nature of the transition states which are different for the two reactions.     

Photochemical Reactions. 126th Communication. Photochemistry of an α, β: δ, ε-unsaturated ketone: 4-(2′, 7′, 7′-Trimethylbicyclo [3.2.0]hept-2′-en-1′-yl)-3-buten-2-one

On ¹n,π*-excitation, the title compound 2 undergoes a photoinduced intramolecular [4 + 2]-cycloaddition affording the tetracyclic enol ether 3 as the only product in 79% yield. The assigned structure of 3 was confirmed by its conversion to the p-nitrobenzoate 6 whose structure was determined by X-ray analysis.     

[3+3] Cyclization reactions of β-nitroenamines and β-enaminonitriles with α,β-unsaturated carboxylic acid chlorides

New indolizidines, quinolizidines, and octahydro-pyrido[1,2-a]azepines of lactam type were synthesized from 2-nitromethylene-pyrrolidine, -piperidine, and -hexahydroazepine, respectively, by [3+3] cyclizations with α,β-unsaturated carboxylic acid chlorides. In the case of quinolizidines, a double bond migration was observed, and explained in terms of amidity percentage. Cyanomethylene-pyrrolidine gave indolizidines of lactam type, while transformations of 1-cyanomethylene-tetrahydoisoquinoline resulted in lactams as well as ketones, when simple open-chain acid chlorides or cinnamoyl chloride were used, respectively.     

Photochemical reactions VII [1]. A ‘type A rearrangement’ in the photolysis of a steroidal α, β-unsaturated lactone

The irradiation of 17 β-hydroxy-2-oxa-androst-4-en-3-one ( 1 ) yield a cyclopropane derivative 2 , which is the result of a rearrangement, formally analogous to the ‘type A rearrangement’ of the enones. Two other products, the dihydroxy compound 5 and the dimer 6 , have also been isolated (Scheme 1).     

β-lithiations of carboxamides. Synthesis of β-substituted-α,β-unsaturated amides

N-Methyl-2-methyl-3-(benzotriazol-l-yl)propanamide, on treatment with butyllithium forms a dianion which on treatment with alkyl and benzyl halides, aldehydes and ketones affords monosubstituted products; with ethyl p-toluate, a lactam is formed. The alkylated derivatives eliminate benzotriazole in the presence of base to afford trisubstituted α,β-unsaturated amides.     

The high resolution mass spectra of α,β-unsaturated and α-chloromercuri-α,β-unsaturated steroidal ketones

The high resolution mass spectra (500 eV) of some α,β-unsaturated steroidal ketones have been studied and compared with the spectra of the corresponding α-chloromercuri ketones. In the latter, the carbon-mercury bond frequently remains intact at the expense of the fission of two carbon-carbon bonds. The abundance of mercury-containing ions allows the use of the mercury atom fingerprint in confirming ring B fragmentation of the steroid nucleus at C(6)–C(7) and C(9)–C(10) for 5α-androst-1-ene-3,17-dione, 1,4-androstadiene-3,17-dione and their 2-chloromercuri derivatives; and at C(7)–C(8) and C(9)–C(10) for 1,4,6-androstatriene-3,17-dione, 1,4,6-androstarien-17 β-ol-3-one and their 2-chloromercuri derivatives. 2-Chloromercuri-1,4,6-androstatriene-3,17-dione and 2-chloromercuri-1,4,6-androstatrien-17 β-ol-3-one also give an abundant ion as the result of ring C fragmentation at C(8)–C(14) and C(11)–C(12), the chloromercuri group being replaced by a hydrogen atom. This ring C cleavage gives the only recognizable distinctive fragmentation ion for 1,4,6-pregnatriene-3,20-dione and 2-chloromercuri-1,4,6-pregnatriene-3,20-dione. For most of the mercurated steroids, the low resolution mass spectra (70 eV) are reported. In these spectra, the fragmentation patterns are similar to those obtained using the higher ionization energy employed for the high resolution spectra.     

Synthesis of α,β-unsaturated ketone from α-iodo ketone using photoirradiation

Irradiation of α-iodo ketone in hexane under a nitrogen atmosphere with a high-pressure mercury lamp (λ>300nm) at room temperature afforded the corresponding α,β-unsaturated ketones in good yield. This reaction affords a new, clean and convenient synthetic method for the α,β-unsaturated ketone.     

Synthesis of 3-substituted 5-arylisoxazoles from α,β-unsaturated oximes

The synthesis of 3-substituted 5-arylisoxazoles from oximes of α,β-unsaturated ketones is studied. The formation of the isoxazole derivatives takes place by cyclization of oximes in the presence of iodine and potassium iodide. The presence of isoxazoline is detected. On the basis of the results a plausible mechanism is suggested.     

Synthesis of α-hydroxy-β-lactams

A convenient synthesis of α-hydroxy-β-lactams has been devised that involves the annelation of an inline with benzyloxyacetyl chloride and triethylamine and subsequent hydrogenolysis in the presence of palladium on carbon. In most cases a cis-β-lactam was obtained. A thioimidate can also be used as the imino component in the annelation reaction but the hydrogenolysis step fails. The annelation of the appropriate thiazoline to a 6-epi-penicillin derivative occurred much more readily with benzyloxyacetyl chloride than with azidoacetyl chloride.     

Photochemical reactions. 148th communication. Photochemistry of acylsilanes: Preparation,photolyses, and thermolyses of α,β-unsaturated silyl ketones

The syntheses, photolyses, and thermolyses of the α,β-unsaturated silyl ketones (E/Z)-7, (E)- 8 , and (E)- 9 are described. On n,π*-excitation (λ > 347 mm), the aforementioned compounds undergo (E/Z)-isomerization followed by γ-H abstraction. The intermediate enols are trapped intermolecularly by siloxycarbenes leading to the dimeric acetals 27A + B, 30A + B , and 31A + B . In addition, the acylsilanes (E/Z)- 7 undergo photoisomerization by δ-H abstraction furnishing the acylsilanes 29A + B . Flash vacuum thermolyses (FVT) of (E/Z)- 7 , (E/Z)- 8 , and (E)- 9 give rise to intramolecular reactions of the siloxycarbene intermediates. Thus, FVT (520°) of (E)- and (Z)- 7 selectively leads to the enol silyl ethers 32 and (E)- 33 , respectively, arising from carbene insertion into an allylic C–-H bond. FVT of (E/Z)- 8 (560°) and (E)- 9 (600°) affords the trienol silyl ethers 34A + B and the cyclic silyl ethers 37A + B , respectively, which are formed by CH insertion of the siloxycarbenes. As further products of (E)- 8 and (E)- 9 , the bicyclic enol ethers 35 and 36 are formed, presumably via siloxycarbene addition to the cyclohexene C?C bond.     

Photochemische Reaktionen 111. Mitteilung [1] Zur Photochemie α, β-ungesättigter γ, δ-Epoxyester I: Singulett- versus Triplettreaktivität

On triplet excitation (E)- 2 isomerizes to (Z)- 2 and reacts by cleavage of the C(γ), O-bond to isomeric δ-ketoester compounds ( 3 and 4 ) and 2,5-dihydrofuran compounds ( 5 and 19 , s. Scheme 1). - On singulet excitation (E)- 2 gives mainly isomers formed by cleavage of the C(γ), C(δ)-bond ( 6–14 , s. Scheme 1). However, the products 3–5 of the triplet induced cleavage of the C(γ), O-bond are obtained in small amounts, too. The conversion of (E)- 2 to an intermediate ketonium-ylide b (s. Scheme 5) is proven by the isolation of its cyclization product 13 and of the acetals 16 and 17 , the products of solvent addition to b . - Excitation (λ = 254 nm) of the enol ether (E/Z)- 6 yields the isomeric α, β-unsaturated ε-ketoesters (E/Z)- 8 and 9 , which undergo photodeconjugation to give the isomeric γ, δ-unsaturated ε-ketoesters (E/Z)- 10 . - On treatment with BF₃O(C₂H₅)₂ (E)- 2 isomerizes by cleavage of the C(δ), O-bond to the γ-ketoester (E)- 20 (s. Scheme 2). Conversion of (Z)- 2 with FeCl₃ gives the isomeric furan compound 21 exclusively.     

Structure and reactivity α,β-unsaturated ethers. II. Cationic copolymerizations of propenyl isobutyl ether

cis- and trans-Propenyl isobutyl ethers were copolymerized with each other and each with vinyl isobutyl ether separately under various conditions. In homogeneous polymerizations a cis-β-methyl substitution on vinyl isobutyl ether apparently enhanced the reactivity, whereas the trans substitution tended to reduce it slightly. In heterogeneous catalysis, on the other hand, a β-methyl group on the vinyl ether, whether cis or trans, greatly reduced the reactivity, probably because of the steric hindrance toward the adsorption of monomers on the catalyst surface. The relative reactivities of cis- and trans-propenyl isobutyl ethers ranged from 2 to 20, depending on the polymerization conditions. The polymer end formed from the cis monomer exhibited special steric effects. It was concluded that even in homogeneous media the rotation of the polymer end around the terminal carbon–carbon bond is restricted.     

The reaction of active and stabilized phosphonium ylides with α,β-unsaturated carbonyl compounds [1]

The active ketenylidene-(2a) or thioketenylidenetriphenylphosphoranes (2b) react with 2-benzylidene-1,3-indandione (1), 5-benzylidenebarbituric acid (11), and 4-benzylidene-1,2-diphenyl-3,5-pyrazolidinedione (16) to give the corresponding pyranones and thioxopyranones (3a,b, 12a,b) and (17a,b), respectively. On the other hand, compounds 1 and 11 can be converted by reaction with the stabilized alkylidenephosphoranes 4a–e into the phosphoranylidenes 6a–e and 13a–e. Moreover, the oxaphosphinins 8 or 14 and the oxazaphosphinins 10 or 15 were obtained when compounds 1 and 11 were allowed to react with the phosphorane 7 and the iminophosphorane 9, respectively. Some of these new organophosphorus compounds are found to have insecticidal and molluscicidal properties against cotton leafworm Spodoptera littoralis larvae and Biomphalaria alexandrina snails. © 1997 John Wiley, & Sons, Inc.