The influence of selected metals and halogens on the electronic system of benzoic acid

The influence of halogens and metals on the electronic system of the aromatic ring in lithium, sodium and potassium complexes with p-halogenobenzoic acids has been investigated by means of ¹³C and ¹H NMR, IR and Raman spectroscopy and semi-empirical calculations. It has been shown that ionic potentials and electronegativities of halogens and metals are the main factors responsible for perturbations of the electronic charge distribution in the ring.     

Association equlibria in acetonitrile solution of tetracyanoquinodimethanides

Trimetric ion (TCNQ)^2?₃ has been discovered in mixed solutions of TCNQ and LiTCNQ in acetonitrile. The estimated association constant isK_T = 5.6 × 10¹⁰ øl² mol^?2.     

Absolute rate constants for some hydrogen atom abstraction reactions by a primary fluoroalkyl radical in water

A combination of laser flash photolysis and competitive kinetic methods have been used to measure the absolute bimolecular rate constants for hydrogen atom abstraction in water from a variety of organic substrates including alcohols, ethers, and carboxylic acids by the perfluoroalkyl radical, *CF(2)CF(2)OCF(2)CF(2)SO(3)(-) Na(+). Comparison, where possible, of these rate constants with those previously measured for analogous reactions in the non-polar organic solvent, 1,3-bis(trifluoromethyl)benzene (J. Am. Chem. Soc, 1999, 121, 7335) show that the alcohols react 2-5 times more rapidly in the water solvent and that the ethers react at the same rate in both solvents. A transition state for hydrogen abstraction that is more reminiscent of an "intimate ion pair" than a "solvent separated ion pair" is invoked to explain these modest solvent effects.     

Reactions of Polycyclic Ketones with Dimethoxycarbene; a Convenient Route for a ‘One‐Pot’ Preparation of Some α‐Hydroxycarboxylic Acid Esters

Polycyclic ‘cage’ ketones, such as pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecan‐8‐one ( 10 ), pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane‐8,11‐dione ( 11 ), and adamantan‐2‐one ( 16 ) were treated with the nucleophilic dimethoxycarbene (DMC; 1 ), which was generated thermally from 2,5‐dihydro‐2,2‐dimethoxy‐5,5‐dimethyl‐1,3,4‐oxadiazole ( 4a ) in boiling toluene. In this ‘one‐pot’ procedure, the α‐hydroxycarboxylic acid ester 12 or a corresponding derivative 15 or 17 was obtained (Schemes 4–7). Additionally, ‘cage’ thione 21 was treated with DMC under the same conditions yielding dimethoxythiirane 22 (Scheme 8). Subsequent hydrolysis or desulfurization (followed by hydrolysis on silica gel) of 22 gave α‐mercaptocarboxylate 25 and the corresponding desulfurized ester 24 , respectively. In all cases, the addition of DMC occurred stereoselectively, and the addition from the exo‐face is postulated to explain the structures of the isolated products.     

Proton transfer reactions from N-H acid [5,10,15,20-tetrakis(pentafluorophenyl)-21-H, 23-H-porphyrin] to strong bases in acetonitrile

Deprotonation of 5,10,15,20-tetrakis(pentafluorophenyl)-21-H, 23-H-porphyrin (PhF₅PorH₂) by various bases has been studied by ¹H NMR and kinetic methods. The kinetic parameters in acetonitrile were defined for proton transfer reactions yielding [NH]⁺ protonated bases and [NHN]⁻ anions with intramolecular hydrogen-bonded chains.     

1,3-Dipole mit zentralem S-Atom aus der Umsetzung von Aziden mit Thiocarbonyl-Verbindungen: Eine unerwartete MeS-Wanderung im Abfangprodukt eines ‘Thiocarbonyl-aminids’ mit Dithiobenzoesäure-methylester

1,3-Dipoles with a Central S-Atom from the Reaction of Azides and Thiocarbonyl Compounds: An Unexpected MeS Migration in the Trapping Product of a ‘Thiocarbonyl-aminide’ with Methyl Dithiobenzoate Reaction of PhN₃ with O-methyl thiobenzoate ( 11a ) and thioacetate ( 11c ) as well as with the dithio esters 11b,d at 80° yields the corresponding imidates and thioimidates 12 (Scheme 3). The formation of 12 is rationalized by a 1,3-dipolar cycloaddition of the azide and the C?S group followed by successive elimination of N₂ and S. In the three-component reaction of 11b , PhN₃, and the sterically crowded thioketone 1a , 1,2,4-trithiolane 13a and 1,4,2-dithiazolidine 3a are formed in addition to 12b (Scheme 4). The heterocycles 13a and 3a are trapping products of 1a and ‘thiocarbonyl-thiolate’ 5a and ‘thiocarbonyl-aminide’ 2a (Ar?Ph), respectively (Scheme 6). These 1,3-dipoles are formed as reactive intermediates. Surprisingly, in the presence of catalytic amounts of acids, the major product is the (methyldithio)cyclobutyl thioimidate of type 14 (Scheme 5), formed by an acid-catalyzed MeS migration in dithiazolidine 17 . A reaction mechanism is proposed in Scheme 7.     

Reactions of Chlorosulfanyl Derivatives of Cyclobutanones with Different Nucleophiles

The reactions of 3‐chloro‐3‐(chlorosulfanyl)‐2,2,4,4‐tetramethylcyclobutan‐1‐one ( 2 ) with N, O, S, and P nucleophiles occur by substitution of Cl at the S‐atom. Whereas, in the cases of secondary amines, alkanols, phenols, thiols, thiophenols, and di‐ and trialkyl phosphates, the initially formed substitution products were obtained, the corresponding products with allyl and propargyl alcohols undergo a [2,3]‐sigmatropic rearrangement to give allyl and allenyl sulfoxides, respectively. Analogous substitution reactions were observed when 3‐chloro‐3‐(chlorodisulfanyl)‐2,2,4,4‐tetramethylcyclobutan‐1‐one ( 3 ) was treated with N, O, and S nucleophiles. The reaction of 3 with Et₃P led to an unexpected product via cleavage of the S? S bond (cf. Scheme 13). In the reactions of 2 with primary amines and H₂O, the substitution products react further via elimination of HCl to yield the corresponding thiocarbonyl S‐imides and the thiocarbonyl S‐oxide, respectively. Whereas the latter could be isolated, the former were not stable but could be intercepted by MeOH (Scheme 4) or adamantanethione (Scheme 5). The structures of some of the substitution products were established by X‐ray crystallography.     

Umsetzung von Diazoessigsäure-ethylester mit 1,3-Thiazol-5(4H)-thionen

Reaction of Ethyl Diazoacetate with 1,3-Thiazole-5(4H)-thiones Reaction of ethyl diazoacetate ( 2a ) and 1,3-thiazole-5(4H)-thiones 1a,b in Et₂O at room temperature leads to a complex mixture of the products 5–9 (Scheme 2). Without solvent, 1a and 2a react to give 10a in addition to 5a–9a . In Et₂O in the presence of aniline, reaction of 1a,b with 2a affords the ethyl 1,3,4-thiadiazole-2-carboxylate 10a and 10b , respectively, as major products. The structures of the unexpected products 6a, 7a , and 10a have been established by X-ray crystallography. Ethyl 4H-1,3-thiazine-carboxylate 8b was transformed into ethyl 7H-thieno[2,3-e][1,3]thiazine-carboxylate 11 (Scheme 3) by treatment with aqueous NaOH or during chromatography. The structure of the latter has also been established by X-ray crystallography. In the presence of thiols and alcohols, the reaction of 1a and 2a yields mainly adducts of type 12 (Scheme 4), compounds 5a,7a , and 9a being by-products (Table 1). Reaction mechanisms for the formation of the isolated products are delineated in Schemes 4–7: the primary cycloadduct 3 of the diazo compound and the C?S bond of 1 undergoes a base-catalyzed ring opening of the 1,3-thiazole-ring to give 10 . In the absence of a base, elimination of N₂ yields the thiocarbonyl ylide A ′, which is trapped by nucleophiles to give 12 . Trapping of A ′, by H₂O yields 1,3-thiazole-5(4H)-one 9 and ethyl mercaptoacetate, which is also a trapping agent for A ′, yielding the diester 7 . The formation of products 6 and 8 can be explained again via trapping of thiocarbonyl ylide A ′, either by thiirane C (Scheme 6) or by 2a (Scheme 7). The latter adduct F yields 8 via a Demjanoff-Tiffeneau-type ring expansion of a 1,3-thiazole to give the 1,3-thiazine.     

八乙墓卟啉和四苯基卟啉合钌（Ⅱ）及锇（Ⅱ）的二氧加合物的红外光谱

ＯＥＰ（八乙基卟啉阴离子）和ＴＰＰ（四苯基卟啉阴离子）合钌（Ⅱ）和锇（Ⅱ）的二氧加合物由ｍａｔｒｉｘ分离技术得到（Ｔ＝２０－４３Ｋ，Ｐ＝１０－５－１０－６ｔｏｒｒ）．为了确定ｖ（Ｏ２）带的归属应用了同位素取代法１６Ｏ２／１８Ｏ２．ＩＲ谱说明对于钌的两种加合物（指ＯＥＰ和ＴＰＰ）都有两种异构体，其Ｖ（１６Ｏ２）频率为：Ｒｕ（ＯＥＰ）Ｏ２，１１４１和１１０３ｃｍ－１；Ｒｕ（ＴＰＰ）Ｏ２，１１６７和１１１４ｃｍ－１．Ｏｓ（ＴＰＰ）Ｏ２只生成一种异构体，ｖ（１６Ｏ２）＝１０９０ｃｍ－１，异构体ｖ（１６Ｏ２）：［Ｒｕ（ＯＥＰ）Ｏ２］，１１４１ｃｍ－１，［Ｒｕ（ＴＰＰ）Ｏ２］，１１６７ｃｍ－１，这些加合物约在１００Ｋ时分解，它们的结构指定为ｅｎｄｏｎ，而异构体［Ｒｕ（ＯＥＰ）Ｏ２］，１１０３ｃｍ－１，［Ｒｕ（ＴＰＰ）Ｏ２］，１１１４ｃｍ－１和［Ｏｓ（ＴＰＰ）Ｏ２］，１０９０ｃｍ－１，在２４０—２７０Ｋ分解，它们的结构指定为桥联二聚体．在加合物中，将ＯＥＰ换成ＴＰＰ引起的钌加合物ｖ（Ｏ２）频率的改变比铁和钴加合物更大．ｖ（Ｏ２）相对强度的变化顺序为：Ｆｅ（Ⅱ）→Ｒｕ（Ⅱ）→Ｏｓ（Ⅱ）．