Collisionally induced dissociation mass spectrometric studies of perfluorinated 1H-heptane,tert-butanol, 2-butyltetrahydrofuran and isopropyl bromobutyl ether

High-energy collision-activated dissociation in connection with mass-analyzed ion kinetic energy spectrometry (CAD/MIKES) was employed to probe the structures of some ions generated by methane chemical ionization (CI) and negative ion chemical ionization (NICI) of the title compounds. CAD/MIKES results show that the [M ? H]^? ion of lH-perfluorobeptane and the [O(CF₂)₄Br]^? ion of perfluoroisopropylbromobutyl ether are stable. The methane CI of these fluorocarbons also showed that the expulsion of HF molecules appears to be a major driving force for further fragmentations.     

An efficient method for converting 17-oxo- into 17-acetyl steroids

A study of certain reaction parameters of the recently described procedure for converting ketones to the corresponding carbonitriles using tosylmethyl isocyanide, has led to a modified method suitable for the efficient synthesis of 17-cyanosteroids. These products readily undergo methylation to give the corresponding 17-acetyl compounds. This two-step conversion of steroidal 17- to 20-ketones proceeds in excellent overall yields, and constitutes a particularly mild and simple alternative method to those hitherto used for this purpose.     

Photochemische Reaktionen. 48. Mitteilung [1]. Photolytische Substitutionen von Aromaten mit α-Sulfonyloxyketonen. Vorläufige Mitteilung

Photo-excited arenes have been found to initiate a substitution reaction in which the sulfonyloxy group of α-sulfonyloxyketones is displaced, and the corresponding β-arylketones are formed. Evidence is presented that the electronically excited arene need not be involved directly in the substitution step. It would seem to be more likely that upon interaction with the sulfonyloxyketone a reactive species derived from the latter is produced which is capable of aromatic substitution.     

Perception of intrusive /r/ in English by native, cross-language and cross-dialect listeners

In sequences such as law and order, speakers of British English often insert /r/ between law and and. Acoustic analyses revealed such "intrusive" /r/ to be significantly shorter than canonical /r/. In a 2AFC experiment, native listeners heard British English sentences in which /r/ duration was manipulated across a word boundary [e.g., saw (r)ice], and orthographic and semantic factors were varied. These listeners responded categorically on the basis of acoustic evidence for /r/ alone, reporting ice after short /r/s, rice after long /r/s; orthographic and semantic factors had no effect. Dutch listeners proficient in English who heard the same materials relied less on durational cues than the native listeners, and were affected by both orthography and semantic bias. American English listeners produced intermediate responses to the same materials, being sensitive to duration (less so than native, more so than Dutch listeners), and to orthography (less so than the Dutch), but insensitive to the semantic manipulation. Listeners from language communities without common use of intrusive /r/ may thus interpret intrusive /r/ as canonical /r/, with a language difference increasing this propensity more than a dialect difference. Native listeners, however, efficiently distinguish intrusive from canonical /r/ by exploiting the relevant acoustic variation.     

Structures of gas-phase C2F 7 + ions

In an ion cyclotron resonance spectrometer, less than 96% of the C₇F ₇ ⁺ cation formed on electron ionization of perfluorotoluene reacts with hexamethyldisilazane. In contrast, the C₇F ₇ ⁺ from perfluoronorbornadiene or perfluorobicyclo[3.2.O]hepta-2,6-diene is nonreactive with hexamethyldisilazane. Collision-induced dissociation results support this dichotomy, although the evidence is not as clear-cut. The reactive ion is assigned the benzyl structure and the nonreactive ion the tropyl structure, on the basis of analogy with the protio cases. By AM1 calculations, the perfluorobenzyl ion is 25 kcal/mol more stable than the perfluorotropyl ion, the opposite of the situation for the protio analogs (? 12 kcal/mol). Ab initio calculations at the 3–21G level agree with the semiempirical energy difference to within 0.4 kcal/mol; at the more appropriate 6–31G*/MP2 level, the perfluorobenzyl cation is 9.7 kcal/mol more stable than the perfluorotropyl cation.     

Fast atom bombardment-induced condensation of glycerol with ammonium surfactants. I: Regioselectivity of the adduct formation

Fast atom bombardment promotes condensation between trimethyl tetradecyl ammonium cations and the glycerol matrix. Bond formation at both the head and tail of the surfactant is demonstrated by low energy collision-induced dissociation (ClD) of deuterium-labeled precursors, with a preponderance of the reaction apparently occurring at the tail. Two distinct ClD pathways are identified for each kind of adduct (head- and tail-attack). Evidence is presented for the detection of distonic radical cations of the surfactant, complexed (solvated) with glycerol.     

Steroidal analogues of unnatural configuration—171: Conformational analysis of 4,4,14α-trimethyl-19(10→9β) ABEo-5α,10α-pregnane-6,11-dione

The cis-transoid-cis steroidal analogue 1 was predicted by force field calculations to have non-chair rings B and C. X-ray structure determination confirmed this result.The conformational effects of various salient features of 1 have been investigated by force field methods.     

Steroidal analogues of unnatural configuration—VII : Total synthesis of 17β-hydroxy-9-methyl-9β, 10α-oestr-4-en-3-one,a novel retrotestosterone isomer

Conjugate methylation of 17β-hydroxy-des-a-oestr-9-en-5-one (1) and the derived 4,5-seco-steroid (6b) afforded the respective 9β-methyl compounds. Base-catalysed alkylation of 17β-hydroxy-9-methyl-des-a-9/gb-oestran-5-one (3a) resulted in attack at C(6); this result was used to prepare the anthrasteroid (5). Ring closure of the 9β-methyl-4,5-seco-steroid (8) derived from 6b afforded 17β-hydroxy-9-methyl-9β,10α-oestr-4-en-3-one (9a). Conjugate methylation of 17β-hydroxyoestra-4,9-dien-3-one (11) resulted in 1,4-addition to the dienone system.     

Steroidal analogues of unnatural configuration—X : Synthesis of 9-methyl-19-nor-9β,10α-progesterone

The reaction of 3,3-ethylenedioxy-9-methyl-9β-oestr-5(10)-en-17-one (4) with tosylmethyl isocyanide and base afforded the 17β- and 17α-carbonitriles (5 and 6). Treatment of the 17β-epimer (5) with methyl lithium gave, after hydrolysis, 9-methyl-19-nor-9β-pregn-5(10)-ene-3,20-dione (8). The same reaction sequence employed on 3,3; 5,5-bisethylenedioxy-9-methyl-4,5-seco-9β,10α-oestr-17-one (12), with subsequent cyclization, yielded the 5β-hydroxy-3,20-diketones (17 and 18) as well as 9-methyl-19-nor-9β,10α-progesterone (19) and its 17α-epimer (20).