Alkylidene Derivatives Research Articles

Alkyl and alkylidene derivatives of titanium supported by carbazole ligation

The bis(benzyl) [(cb) 2 Ti(CH 2 Ph) 2 ] 1 and alkylidene bridged dimer [(cb) 2 Ti(µ-CHSiMe 3 ) 2 Ti(cb) 2 ] 3 are formed by adding carbazole (Hcb) to the tetraalkyls [TiR 4 ] (R = CH 2 Ph, CH 2 SiMe 3 ); the reaction of 1 and 3 with 2,6-dimethylphenyl isocyanide leads to organometallic products containing new carbon–carbon bonds.

Stereospecific synthesis of naturally-occurring 4-alkylideneglutamic acids, 4-alkylglutamates and 4-alkylprolines 1

The enaminone 4, prepared from (2S)-pyroglutamic acid, has been found to react in an apparent 1,4-manner with DIBAL and Grignard reagents to afford a variety of alkylidene derivatives 8 which, except for the vinyl derivatives 8e, are formed only as the (E)-isomers. Three of these have been converted to the 4-alkylideneglutamic acids, 1, 2 and 3, which are identical to known natural products, the synthesis confirming 2 and 3 as the E-isomers. Catalytic reduction of the 4-alkylidenepyroglutamate derivatives 8 is stereospecific and affords an effective route to (2S,4S)-4-alkylglutamic acids and (2S,4S)-4-alkylprolines. Cuprate addition to the enone 5 affords access to the (2S,4R)-epimer 15 and carbene addition allows cyclopropylglutamic acids 32 and 33 to be prepared.

ChemInform Abstract: Investigation of Isothiocyanate Addition to Alkylidene Derivatives of Malononitrile and Cyanoacetic Acid Esters.

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Synthesis of naturally-occurring 4-alkylideneglutamic acids

The enaminone ( 4), prepared from (2S)-pyroglutamic acid, has been reacted with Grignard reagents to afford a variety of (E)-alkylidene derivatives ( 8). Three of these have been converted to the 4-alkylideneglutamic acids, ( 1), ( 2) and ( 3), which are identical to known natural products, ( 2) and ( 3) being the E-isomers.

Investigation of isothiocyanate addition to alkylidene derivatives of malononitrile and cyanoacetic acid esters

AbstractAddition of arylisothiocyanates to active methylene compounds leads to a variety of compounds depending on the structure of the starting material and conditions used to conduct the addition. Addition of arylisothiocyanate to 1c leads to a pyrido[2,3‐d]pyrimidine resulting from addition of a second mole of cyanate to the initial adduct. Addition of arylisothiocyanate to 1b led to a mixture of pyridine and thiopyran adducts, while addition to 1a led to open chain structures.

New Synthesis of Substituted QuinolineN-Oxides via Cyclization of Alkylideneo-Nitroarylacetonitriles

Substituted quinoline N-oxides are prepared via base induced cyclization of alkylidene derivatives of o-nitroarylacetonitriles which are readily available via the vicarious nucleophilic substitution cyanomethylation of nitroarenes followed by the Knoevenagel condensation

Efficient Olefinaton with a-Alkyl Cyclic Phosphonamides

A variety of acyclic and cyclic aldehydes and ketones can be converted into the corresponding alkylidene, benzylidene and methoxycarbonyl alkylidene derivatives by treatment with 1,3,2-diazaphospholidine-2-alkyl-1,3-dimethyl 2-oxides (α-alkyl cyclic phosphonamides) under mild conditions. This olefination method is particularly useful in the case of enolizable carbonyl compounds

Reactions of highly electrophilic polyfluoro unsaturated compounds with pyrazole derivatives

Pyrazole derivatives were hydroxyalkylated at the C4 atom by hexafluoroacetate and methyl trifluoropyruvate. The products of the hydroxyalkylation were dehydrated to the corresponding alkylidene derivatives which were reacted with nucleophiles. Dicyanoethylenes, obtained from polyfluorocarbonyl compounds, alkylated pyrazol-5-ones with the formation of pyrazolopyran derivatives.

Ring-ring tautomerism

The superposition within a single molecule of competing ring-chain tautomeric pairs, the minimum structural requirement of which is the presence of one nucleophilic (OH, NH, SH, etc.) and two electrophilic (C=N, C=O, etc.) centers or the reverse, is a method of constructing ring-ring or ring-chain-ring tautomeric systems. On the basis of the structural characteristics of alkylidene derivatives of thiohydrazides, thiosemicarbazides, thiocarbonohydrazides and amidrazones, bis-hydrazones, bis-oximes, and oximohydrazones of 1,3-dioxo compounds, it has been possible to realize for the first time heterocyclic, tautomeric combinations of pyrazoline—isoxazoline, isoxazoline—1,3,4-thiadiazoline, pyrazoline—1,3,4-thiadiazoline, 1,3,4-thiadiazoline-1,2,4-triazolidene, 1,2,4-triazolidene—1,2,4,5-hexahydrotetrazine, 1,2,4,5-hexahydrotetrazine—tetrahydropyran, tetrahydropyran—1,3,4-thiadiazoline, etc.

Monocyclopentadienyl alkyl alkylidene niobium(V) and tantalum(V) complexes. X-ray crystal structure of Ta(η 5-Cp′)(CH 2SiMe 3) 2(CHSiMe 3)

Reactions of monocyclopentadienyl complexes M(η 5-Cp′)Cl 4 with trimethylsilylmethyl lithium leads to the formation of alkylidene derivatives M(η 5-Cp′)(CH 2SiMe 3) 2(CHSiMe 3), where M = Nb ( 1); Ta ( 2); Cp′= C 5Me 5 and M = Ta; Cp′ Me 3Si(C 5H 4) ( 3), 1,3-(Me 3Si) 2(C 5H 3) ( 4). The new complexes were characterized by 1H and 13C NMR spectroscopy and the molecular structure of 2 was studied by X-ray diffraction methods.

Ring-chain tautomerism of substituted hydrazones. 22. Synthesis, structure, and oxidation of alkylidene derivatives of 2-aminoethylhydrazines

Alkylidene derivatives of 2-aminoethylhydrazines exist in solutions either as 2-aminoethylhydrazones or as the ring-chain tautomeric mixtures of the hydrazone—perhydro-1,2,4-triazine depending on the structure. The oxidation of perhydro-1,2,4-triazines leads to the formation of 2,3,4,5-tetrahydro-1,2,4-triazines.

Herstellung chiraler elektrophiler Glycin‐ und (E)‐2,3‐Dehydroaminosäure‐Derivate aus 2‐t‐Butyl‐3‐methyl‐4‐oxo‐1‐imidazolidincarbonsäure‐t‐butylester (Boc‐BMI)

Preparation of Chiral Electrophilic Glycine and (E)‐2,3‐Dehydroamino Acid Derivatives from t‐Butyl 2‐t‐Butyl‐3‐methyl‐4‐oxo‐1‐imidazolidinecarboxylate (Boc‐BMI)Boc‐BMI, the compound specified in the title, is brominated under radical‐chain conditions (NBS/AIBN) to give trans‐bromo‐BMI 2, which is highly reactive in nucleophilic substitutions [see the 5‐carbo‐ and ‐hetero‐substituted (N, O, S, P) 2‐t‐butyl‐3‐methylimidazolidinones 4 – 23 and Tab. 1]. The substitutions occur preferentially with inversion of the configuration, the mechanism being not clear at all. – The Boc‐BMI dimethyl phosphonate 23 (Michaelis‐Arbusov product from 2) reacts with aldehydes (15 examples) to give preferentially (E)‐5‐alkylidene‐imidazolidinones, chiral α‐aminoacrylic acid derivatives which are available in either the R or the S form, see 24 – 38 (Tab. 2). Best yields and highest (E) selectivities (> 25:1), with short reaction times, are obtained by using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene. (DBU)/LiBr in dry THF in a very special variant of the Horner olefination. α‐Branched, racemic aldehydes may give alkylidene derivatives with efficient kinetic resolution (38). Some speculations are made about the mechanism and the observed stereochemical outcome of the reaction (I, J, K). A comparison is made with other chiral electrophilic glycine (A – C) and α,β‐dehydroamino acid derivatives (D, E), as well as with other methods for the preparation of enantiomerically pure methylenedioxolan‐, ‐oxazolidin‐, and ‐imidazolidinones (H), containing an α,β‐unsaturated carbonyl system.

Stereoselektive Umsetzungen von rac‐, (R), oder (S)‐5‐Alkyliden‐2‐t‐butyl‐3‐methyl‐4‐oxo‐1‐imidazolidincarbonsäure‐t‐butylestern (chirale 2,3‐Dehydroaminosäure‐Derivate) und Herstellung einiger nichtproteinogener Aminosäuren

Stereoselective Conversions of t‐Butyl rac‐, (R)‐, or (S)‐5‐Alkylidene‐2‐t‐butyl‐3‐methyl‐4‐oxo‐1‐imidazolidinecarboxylates (Chiral 2,3‐Dehydroamino Acid Derivatives) and Preparation of Some Nonproteinogenic Amino AcidsThe reacivity of the alkylidene derivatives 1–11 specified in the title and prepared in two operational steps from commercially available Boc‐BMI and aldehydes is investigated. – According to high‐field 1H‐NMR analysis of the crude products, additions of HH and DD (catalytic hydrogenation, products 12–20, of RH (BF3‐activated R2CuLi/LiI and protonation, products 21–29), and of Cl2C (CHCl3/NaOH, products 33, 34) occur with complete selectivity from the face opposite to the t‐butyl group. The doubly unsaturated carbonyl derivative 11 reacts with dibutyl cuprate in the δ position, again with formation of a single diastereomer 32, while trifluoroethylidene‐Boc‐BMI 3a is reduced to the difluoro analogue 30 by this cuprate. – Li dienolates are generated by deprotonation with LDA of the ethylidene (2a) and butylidene compound 4a; subsequent alkylations (with primary and secondary halides, products 35–41) and hydroxyalkylations (with aldehydes, products 42–44) lead to single products of electrophilic attack in the a carbonyl position (C‐5 of the imidazolidinone ring) under kinetic control. On the other hand, reaction of the 2a‐derived dienolate with benzaldehyde under equilibrating conditions furnishes the four possible (E/R, E/S, Z/R, and Z/S) γ adducts 45–48. – A combination of methods – 1H‐ and 13C‐NMR spectroscopy, NOE measurements, spectroscopic analogies, chemical correlation (with authentic samples or by spectroscopic or optical comparison), and X‐ray analysis (Table 1, Figure 1, Schemes 1 and 2) – is used to assign the product configurations and thus the stereochemical course of the reactions. Some unusual amino acids (50–52, 54, 55) are prepared by hydrolysis of the corresponding imidazolidinones.

ChemInform Abstract: Reactions of Titanium Derivatives of Some CH‐Acids with Carbonyl Compounds. Part 1. Crotonic Condensation with Titanium Derivatives of Malonic Ester, Cyanoacetic Ester and Malononitrile.

AbstractThe condensation of the titanium derivatives (I) with aldehydes (II) gives much higher yields of the alkylidene derivatives (III) than the Knoevenagel reaction (15 examples).

ChemInform Abstract: Thioalkylation of Meldrum′s Acid: Protected Alkylidene Derivatives of Isopropylidene Malonate.

AbstractThe title reaction of Meldrum's acid (I) yields the adducts (IV) or (XIII).

Reactivity of dimethyl N-(ethoxycarbonylmethyl)iminodithiocarbonate with carbonyl compounds in basic medium

The reactivity of dimethyl N-(ethoxycarbonylmethyl)iminodithiocarbonate with aromatic aldehydes and reactive ketones has been studied. Ethyl 3-aryl-2-(methylthiocarbonylamino)acrylates (1) are obtained with aromatic aldehydes by ring-opening isomerization of the intermediate 5-aryl-4ethoxycarbonyl-2-methylthio-4,5-dihydro-1,3-oxazoles (2). With ketones it has been shown that the cycloalkanones give rise to the corresponding alkylidene derivatives by a reaction path identical with that of aromatic aldehydes, whereas hexafluoropropanone and 1,1,1-trifluoropropanone display duality in acting as both acylating reagents and carbonyl compounds.

Chemical transformation of protoberberines. XV. A novel and efficient method for the introduction of alkyl groups on the C-13 position in the protoberberine skeleton.

The Wittig reaction of 8, 14-cycloberbin-13-ones (4), derived from the corresponding protoberberine alkaloids (2), with methylenetriphenylphosphorane afforded 13-methylene-8, 14-cycloberbines (5). Irradiation of 5 with a 100 W high pressure mercury lamp effected photochemically-induced electrocyclic fission of the aziridine ring to yield 13-methylberberine (1a), dehydrocorydaline (1b), and corysamine (1c) in high yield. Introduction of ethyl and propyl groups on the C-13 position in 2 was also conveniently achieved via photochemical reaction of the corresponding alkylidene derivatives (8 and 9, respectively).

Thioalkylation of Meldrum's Acid: Protected alkylidene derivatives of isopropylidene malonate

AbstractThioalkylated Meldrum's acid is easily by treatment of Meldrum's acid with an aldehyde and thiophenol in the presence of catalytical amounts of piperidinium acetate (→1–6, Table 1). The adducts 1–6 are crystalline, stable compounds and they can be caused to react directly with nucleophiles and dienes (see 3→7–12, Scheme 1). The regeneration of the parent olefin is effected thereby by simply dissolving the adduct under neutral or basic conditions. Extension of this method to thiocarboxylic acids allowed the preparation of the corresponding formaldehyde derivatives 13 and 15 (Table 3).

Alkylidene derivatives of syn-sesquinorbornatriene. 13C NMR and theoretical analysis of homoconjugative orbital interactions

Despite downward folding of the central π linkage in 7 and 13, polarization of the exocyclic olefinic bonds does not surpass that seen in 1 and is not at all affected by cumulative carbomethoxy substitution of the peripheral unsaturated centers as in 9 and 10.

ChemInform Abstract: SYNTHESIS AND RING‐CHAIN TAUTOMERISM OF SALTS OF ALKYLIDENE(ARYLIDENE) DERIVATIVES OF AMIDRAZONES

A number of salts of alkylidene (arylidene) derivatives of amidrazones was obtained by the reaction of S-methylthioamidium iodides with hydrazones of monocarbonyl compounds. According to the 1H and 13C NMR data, these compounds in solutions are capable of ring-chain tautomerism of the 1-alkylideneamidrazone-1,2,4-triazoline type. The position of the equilibrium is determined chiefly by steric interactions of the substituents attached to the C-N2 bond.