Oxidations by thionyl chloride. II. 3-Thietanones from ketones

Abstract

Figure 1. Photostationary states of 2-benzal-5-methylcyclopentanone (1) as a function of sensitizer triplet energy: •, unselective sensitizers; O, selective sensitizers.predicts the selectivities of sensitizers with £T > 59 kcal/ mol but fails to predict that all lower energy sensitizers are unselective.1 234 This result is predictable if there is an isomer of 1 having a ~59-kcal/mol T2 state with , * character. Lower energy potentially selective sensitizers would then have insufficient energy to populate the T2 state, and exothermic energy transfer would ensue causing population of the -, * hydrogen abstraction intermediate. The observed occurrence of isomerization even with the lower energy sensitizers could be due to competing nonvertical energy transfer to give a distorted 3( , *) state or to isomerization of the 3( , *) state.The changes in the photostationary ratios on reducing the triplet energies of the sensitizers also suggest a 2-, * state of 1. The decrease in the trans-cis ratio with lower energy selective sensitizers suggests that the cis-7r,7r* triplet is more energetic than the trans-, * triplet and therefore is populated less efficiently on lowering the sensitizer energies. The increase in the trans-cis ratio with lower energy unselective sensitizers implies that, conversely, with these sensitizers the efficiency of excitation to the trans-, * triplet falls off faster than to the cis-, * triplet. Analogy with sensitization of oxygen to its 4 8+ state suggests that excitation to T2 states may fall off rapidly with sensitizers having energies up to 10 kcal/mol above the T2 energy.5 Thus if the , * triplet of trans-1 is a T2 state, excitation to this state with unselective sensitizers could become inefficient earlier than excitation of cz's-1 to its higher energy , * state.(4) This is strictly true only if the nearly identical triplet energies given for the two phenylnaphthalene sensitizers are reversed.(5) D. R.

Oxidations by thionyl chloride. Mechanism of 3-thietanone formation. I

“…A few years ago we reported the oxidative conversion of /3-aryl carboxylic acids and certain ketones to benzo [b]thio-phenes2 and of methyl ketones to 3-thietanones. 3 The unusual nature of these products and the generality of the reactions prompted us to examine the mechanism by which these products were being formed. The results of our investigation of the benzothiophene case have been reported.2…”

Oxidations by thionyl chloride. VI. Mechanism of the reaction with cinnamic acids

“…Sulfenyl chloride 12, an approximately 1:1 mixture of diastereomers, revealed infrared absorption at 5.56 and 5.67 µ and NMR signals at r 5.10 (q, 1 H, J = 6.5 Hz), 8.20 and 8.27 (two sets of d, 3 H, J = 6.5 Hz). Sulfenyl chloride 12 apparently eliminates sulfur dichloride when treated with pyridine hydrochloride and thionyl chloride at reflux, furnishing 13 Treatment of 3 with a catalytic amount of pyridine hydrochloride at 130°for 5 hr afforded a mixture of 3 (32%), 4 (38%), and 5 (30%) as revealed by NMR spectroscopy. Fractional crystallization of the mixture from carbon tetrachloride afforded benzo [5 ] thiophene 4 in 36% yield.…”

“…In the presence of a catalytic amount of a tertiary amine, thionyl chloride generally oxidizes carboxylic acids and ketones at a carbon atoms to form a-chloro-a-chlorosulfenyl derivatives and their subsequent reaction products. Thus, 3-phenylpropanoic acid (1), for example, when treated with an excess of thionyl chloride and a small amount of pyridine, can be converted to sulfenyl chloride 2, which then undergoes further reaction to form benzo [6]thiophene 4 and -chlorocinnamoyl chloride (5) via intermediate 3 (eq l).3 Another example is the conversion of methyl ketones to 3-thietanones 7 presumably through intermediates 6, that offered a one-step synthesis of the four-membered hetereocycles (eq 2).4…”

Reaction of nitriles with thionyl chloride in the presence of hydrogen chloride. Formation of sulfinyl and sulfenyl chlorides and phenyl cyanosulfine

“…The latter, however, appear more susceptible to inhomogeneous current distributions which give rise to spurious giant apparent conductivities. 15,16 We conclude that most of the variation in conductivity among samples of TTF-TCNQ is due to lattice imperfections rather than chemical purity.…”

“…In the case of nitriles with two a hydrogens, the initially formed sulfinyl chloride further reacts with thionyl chloride to give the sulfenyl chloride 7 possibly via the Pummerer type reaction proposed by Krubsack et al for the chlorosulfinylation of acid chlorides and ketones by thionyl chloride. 15,16 In the case of phenylacetonitrile, phenyl cyanosulfine ( 11) is also produced, the yield of which is very low as a result of suppression of dehydrochlorination from sulfinyl chloride 2 (R1 = CgHs; R2 = H) when a large excess (6 equiv) of hydrogen chloride is used. At a glance, sulfine 11 seems to be in equilibrium with sulfinyl chloride 2 (R1 = CgHs; R2 = H).…”