Doubly Metalated 2‐Propene‐1‐thiol: Thioacrolein Dianion

Abstract

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 '

Iron and cobalt complexes of thioacroleins derived from thietes

“…Anal. 1 -Cycloheptenethioaldehydeiron Tricarbonyl (6). In a procedure identical with that for the preparation of 5, diiron nonacarbonyl (2.6 g, 7.15 mmol) and 8-thiabicyclo[5.2.0]-l(9)-octene3 (0.99 g, 7.15 mmol) gave orange-red crystals of complex 6: mp 28-29°.…”

“…5 The dianion of thioacrolein, obtained by treatment of allyl mercaptan with zz-butyllithium, has been investigated recently. 6 Monomeric Iron Complexes. Treatment of thietes 1-3 with diiron nonacarbonyl (thermal) or with iron pentacarbonyl (photochemical) gave complexes [4][5][6], respectively, of thioacroleins, whose structures are based on an x-ray analysis of triphenylphosphine complex, 7, derived from 4 by replacement of one carbon monoxide ligand.1•7 A triethoxyphosphine complex (8) also was prepared.…”

“…6 Monomeric Iron Complexes. Treatment of thietes 1-3 with diiron nonacarbonyl (thermal) or with iron pentacarbonyl (photochemical) gave complexes [4][5][6], respectively, of thioacroleins, whose structures are based on an x-ray analysis of triphenylphosphine complex, 7, derived from 4 by replacement of one carbon monoxide ligand.1•7 A triethoxyphosphine complex (8) also was prepared. Thiobenzophenones, which may be considered as a special variety of ,/3-unsaturated thio ketones, behave differently on complexation with metals: an ortho hydrogen of the aromatic ring is replaced by the metal.…”

1,2-Benzothiaborolide: A New Heteroaromatic Analogue of Indenyl

“…The key step in the synthesis of 3 involves the double deprotonation of 2-methylbenzenethiol (7) by BuLi to form 8 (Scheme 1). A variety of analogous 1,4-dilithio compounds have been prepared by dilithiation, [3][4][5][6][7] but to the best of our knowledge this reaction has never been reported for 7. 8 is a useful precursor for five-membered-ring sulfur heterocycles.…”

“…Solid-state structure of 12. Selected distances (Å): Ru-S ) 2.4395(12); Ru-B ) 2.445(5); Ru-C(7) ) 2.311(4); Ru-C(6) ) 2.217(4); Ru-C(1) ) 2.213(4); S-B ) 1.894(5); B-C(7) ) 1.604(7); C(7)-C(6) ) 1.467(7); C(6)-C(1) ) 1.436(7); C(1)-S ) 1.744(5); B-N ) 1.423(7).…”