Aliphatische, cycloaliphatische und aromatische Thiole liefern in Gegenwart von Lewis-Saure mit Orthoameisensaure-trimethylester in guten Ausbeuten die offenkettigen, monocyclischen und bicyclischen Trithioester 4a-s und 8. Methoden zur gezielten Herstellung von Derivaten mit zwei verschiedenen RS-Gruppen werden beschrieben. Die Orthotrithioester werden bei -70" in T H F durch Butyllithium quantitativ zu 1 metalliert. Aus den Metallderivaten 1 und Methyljodid entstehen die 1.1 .I-Tris-mercapto-athane 5. Zerfall von 1 liefert die Tetrakis-mercapto-athylene 6; die alkylsubstituierten Verbindungen 1 zerfallen schon bei Temperaturen zwischen -50 und -20"; um Tetrakis-arylmercapto-athylene herzustellen, mu0 man die entsprechenden Verbindungen 1 mit Cyclohexenoxid ,,zersetzen". Thiolierungen von metallierten Formaldehyd-dithioacetalen und Orthotrithioameisensaureestern mit Disulfiden fuhren zu den Tetrakis-mercapto-methanen 7, 9, 17, 18 und 19.Aliphatic, cycloaliphatic, and aromatic thioles are converted to orthotrithioesters in good yields by treatment with trimethyl orthoformate in the presence of Lewis acids; open chain, monocyclic and bicyclic derivatives 4a-s and 8 are prepared. Methods for the unambiguous synthesis of tristhiomethanes with two different RS-groups are described. Metalated orthotrithioformates 1 are obtained from 4 and n-butyllithium in T H F at -70" as shown by quantitative isolation of the 1.1.1-tristhioethanes 5 after reaction with iodomethane. The organometallic compounds 1 decompose to give tetrakisthioethylenes 6. Decomposition takes place ,,thermally" between -50 and -20" in the case of open chain alkyl derivatives 1 while the aryl analogs must be ,,decomposed" with cyclohexene epoxide. The tetrakisthiomethanes 7, 9, 17, 18 and 19 are prepared from metalated formaldehyde dithioacetals or orthotrithioformates and disulfides. 1 ) Die vorliegende Arbeit ist ein Teil der Habilitationsschrift von D. Seebach, Univ. Karls-2) ruhe 1969, der Diplomarbeit (Univ. Karlsruhe 1971) und der Doktorarbeit (Univ. GieRen) von K.-H. CeiJ. Vorlaufige Mitteil.: D. Seebach, Angew. Chem. 79, 468 (1967); Angew. Chem. internat. Edit. 6, 442 (1967). 1 2 3 4 5 6 7 als Losungsmittel untersucht worden6,7). Wir konnten im Falle von 1, R = C6H5, zeigen, da8 sich T H F als Losungsmittel besser eignet, und daB das studierte Carbenoid ungewohnliche Eigenschaften besitzto, deren Abhangigkeit von der Art der Substituenten Ziel weiterer Untersuchungen war. Es wird hier uber die Darstellung von Orthoestern 4 mit den verschiedenartigsten aliphatischen, cycloaliphatischen und aromatischen Gruppen R, uber die Erzeugung entsprechender Lithiumverbindungen 1 und deren Umwandlung in Orthoessigester 5 (mit CH3J), Tetrakis-mercapto-athylene 6 (durch Zerfall) und Orthokohlensaureester 7 (mit Disulfiden RSSR) berichtet. A) Herstellung der Orthotrithioameisensaureester 41. Mit drei gleichen Cruppen R Durch die hohe Nucleophilie der Mercaptane sind Orthotrithioester allgemein leichter zuganglich als die Sauerstoffanalogen : sie bilden sich un...

Die Magnesiumderivate des Thioacrolein-Dianions (1 b) und des doppelt deprotonierten Methallylmercaptans werden aus den entsprechenden Lithioverbindungen und MagnesiumbromidEtherat erhalten und reagieren mit normalen und a, a-ungeslttigten Aldehyden und Ketonen zu a-1,2-Produkten 2 -5 (nach der Methylierung), siehe Tab. 1 und 2. -Aus den Diastereomerengemischen 2, 3 entstehen durch S-Methylierung und Eliminierung E/Z-isomere VinyL(6) und Divinyloxirane (7). -Oxid-Cope-Umlagerung der Methylthio-hexadienole 3, 5 mit Kaliumhydrid in T H F oder THF/HMPT fiihrt zu Thioenolethern 8 von 6-Ketoaldehyden (s. Tab. 3 und 4). Durch die in Schema 1 gezeigten Versuche wird bewiesen, daB die Umlagerung konstitutions-und stereoselektiv verlauft, also nicht uber aquilibrierende Dissoziation/Rekombination. Doubly lithiated ally1 (1 a) and methallylmercaptan and MgBr,.etherate furnish reagents (cf. 1 b) which add to aldehydes and ketones, including a, P-unsaturated ones, to give the a-l,2-products 2-5 after methylation (see tables 1 and 2). The isolated hydroxythioethers contain less than 10% y-adducts (cf. A in table 1 ) ; with enones no Michael-addition occurs; if there are two centers of chirality in 2-5, diastereomeric mixtures are formed. -With CH31 or Mecrwein reagent the hydroxysulfonium salts G (OH instead of 0') are generated which give E I Z mixtures of vinyl and divinyl oxiranes 6 and 7, respectively, upon treatment with aqueous base in a two-phase system. -Oxide-Cope rearrangement of the potassium alkoxides of the 1,5-hexadienes 3, 5 in THF, HMPT, or mixtures of the two solvents produces ketoaldehyde thioenol ethers 8 in good yields (tables 3 and 4). The a-and y-1,2-adducts (3d. 10) rearrange with high constitutional and stereochemical selectivity to the ketones (8b, l l ) , see scheme 1 . This provides evidence for a pericyclic rather than ionic (dissociation/recombination) mechanism of the oxide-Cope rearrangement of the alkoxides 3 , s (0' instead of OH). -Hydrolysis of the products 8 of rearrangement and aldol ring closure leads to cyclopentenyl ketones 14 in modest overall yields. For the thioenol ether hydrolysis a two step procedure (8 .+ 13 + 12) is recommended. -Scheme 2 demonstrates the synthetic equivalence of the organometallic reagent 1 b with allylidene and propionaldehyde d'-synthon.f" Verlag C'hcmie. GnihH, I)

4) Thermochemical increment calculations do not reveal any diffcrenccs in the molar heats of formation AH:' of ( 1 ) and (-7) even aftel-taking special account of the H/H interactions (staggered or eclipsed). Since the adducts ( I ) and ( 2 ) have (almost) equal energy contents it does not appear surprising that the same activation energies are found for the 1.3 shift and cycloreversions (within the limits of error) if the (possibly polar) diradical (3) is formed initially without any change in multiplicity. The "allowed" reaction (2) +( ( 4 ) + ( 5 ) ) is not energetically favored. and the differences in the reaction rates are due almost exclusively to thedifferent frequency factors (cf. formula scheme). The symmetry-corrected rate constant ( k l + k11)/2 is 5.6 times greater than kttl (see above). This kinetic disadvantage of the retro-Diels-Alder reaction suggests that the eclipsed arrangement of benzhydrylic and allylic hydrogen atoms in ( I ) (dihedral angle cu. 12""0'; 'H-NMR coupling constant J = 9.0 Hz"') enhanccs the probability of cleavage of thc C--C bond compared to the staggered arrangement in ( 2 ) (60 r t O i : 3.0 Hzl"). In both cases the intermediate (3) is formed which has the possibility of rotation about the exocyclic C--C bond. and finally the products ( ( 4 ) + ( 5 ) ) and (2) are obtained in the ratio Xl~/kl=80.5/19.5. In addition, molecular models prcdict that the stabilization route ( 3 ) + ( I ) must also be operative. This reaction, which cannot be detected by UV spectroscopy mainly because the primary reaction of (I) on pyrolysis is ca. 11 times faster, would become of preparative significance ifthedecomposition ofthe [4+4] adduct ( I ) could beprevented : selective irradiation of anthracene ( 4 ) in cyclopentadiene ( 5 ) (0 C) affords a photointermediatel'l which is likewise assumed to have formula ( 3 ) (presumably in similar rotational and vibrational states). Kinetically controlled reaction then yields ( I ) and (2) in the ratio 58/42'"'. The utility of direct comparison of thermal and photochemical two-step reactions is apparent from the results obtained on irradiation of adduct ( 1 )I1 'I. The "allowed" reactions afford 80 '

are apparently not registered owing to the low solubility of (3).In addition to HV(C0)3(n-C6H3(CH3)3)151 we now have another defined hydrido complex of vanadium in HV(PF,),. Whether the above synthetic route is suitable for the preparation of hexakis(trifluorophosphane)metal hydrides of higher homologs of vanadium which may also be capable of existence is currently under study.Experimental: All operations are performed under nitrogen; the solvents are purified in the usual way and saturated with nitrogen.Bis (diglyme) sodium hexakis (trifluorophosphane) vanadate (1) A solution of ( 1 ) (7.00 g, 13.7 mmol) in diglyme (150 ml) is cooled to -45°C and saturated with PF, in an irradiation apparatus (Duran 50) with internal cooling and an external vacuum jacket. The vigorously stirred reaction mixture is irradiated for 24 h with an external high-pressure mercury arc lamp (Q 600 Hanau) until evolution of CO is no longer observed. The solution must be resaturated several times with PF3 during the reaction. The solvent is then removed in a high vacuum and the residue washed twice with light petroleum. The product thus obtained is sufficiently pure for the synthesis of (3). Analytically pure samples are obtained by recrystallizing from diglyme with light petroleum. Yield :(2) 11.64g (98%). Hexakis(trifluorophosphane)vanadiwn hydride ( 3 )Compound (2) (5.00g, 5.7 mmol) and crystalline orthophosphoric acid (50g, 510mmol) are heated to 60°C in a flask fitted with a cold trap. The resulting hydrido complex is immediately drawn off into the cold trap (-196°C) by a high vacuum and then sublimed at 50"C/10-z torr over P4010 in order to remove residual traces of water. Yield 2.26 g (68 YO) of ( 3 ) .

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