Naphthyl vinyl sulfide 5 is prepared by acid-catalyzed addition-dehydration of 2-naphthalenethiol to ethyl acetoacetate. Photocyclization-rearrangement of 5 gives dihydrothiophene 6a, which is desulfurized to 7a; saponification of 7a and polyphosphoric acid cyclodehydration of the resulting acid 7c gives 2-ethyl-l-acenaphthone. A series of 2-thioaryloxyenones lla-k is prepared by reaction of the appropriate aromatic thiol with isophorone epoxide in the presence of base. Photocyclization-rearrangement of 11 gives dihydrothiophenes 12 in high yield; desulfurization of 12 with Raney nickel gives 3-arylcyclohexanones 13, while reductive cleavage of 12 with zinc in acetic acid gives an ortho-substituted benzenethiol isolated in hemithioketal form 14. Thioaryloxyenones 18, 19, 20a, and 20b are prepared from the appropriate thiol and the epoxide derived from 2-cyclopenten-l-one, A1(9)-octal-2-one, and A4(5)cholesten-3-one, respectively; these undergo photocyclization-rearrangement to give dihydrothiophenes. With fused ring thioaryloxyenones 19 and 20 only a cis-decalone ring fusion results; none of the corresponding trans isomer is detected. Acyclic thioaryloxyenones are not available via the epoxy ketone route; 3-thiophenoxy-4-methyl-3-penten-2-one (26) is prepared by reaction of 3-chloro-2,4-pentanedione with thiophenol 'in pyridine to give 3-thiophenoxy-2,4-pentanedione (24), followed by treatment with excess methylmagnesium bromide and finally acetic anhydride at reflux temperature. Irradiation of 26 gives dihydrothiophene 39 in 84% yield. A direct annelation route to 19 involves reaction of thiophenoxymethyl vinyl ketone (44) with the pyrrolidine enamine of cyclohexanone 45. With modification of the annelation reagent, a variety of multicyclic ring systems with angular aromatic substituents should be available by the sequence cycloalkanone annelation-photocyclization-desulfurization. Dihydrothiophene 12a undergoes regioselective alkylation of the equilibrium enolate to give 12b, which is converted to sulfone 46c. Reaction of 46c with 1 N sodium hydroxide gives the ketone cleavage product carboxylic acid 48, demonstrating that highly substituted aryl annelated dihydrothiophene 1,ldioxides are available by methodology based on heteroatom directed photoarylation of aryl vinyl sulfides.W e wish to describe a new aromatic ring substitution process called heteroatom directed photoarylation. T h e methodological term heteroatom directed photoarylation is intended to characterize photochemically initiated, electrocyclic reactions originating from arrangements of a n available electron pair in a heteroatom and the electrons from a t least one aromatic B bond. The synthetic potential of the generalized photoreaction A -B, one example of heteroatom directed pho-B toarylation, will be presented in this report. W e will show that the photoreaction is quite general, proceeds with high chemical and photochemical efficiency, and is compatible with a wide variety of functional groups within the molecular system. O u r studies began...

No abstract

Die Photolyse der Aryloxy‐enone (Ia), (Ib) und (II) wird untersucht.

133 (100), 117 (12), 105 (13), 91 (14), 77 (8), 51 (6), 41 (11), 39 (12), and 29 (12). The ir and nmr spectra were in complete agreement with those of 2,3-dimethylcumene. A vpc collected sample showed the same spectral properties.5

Thermal rearrangement of 10-isobornyl sultone (1) affords exo-camphene sultone (2). In the early stages of the rearrangement endo-camphene sultone (8) can be isolated. The stability order for the sultones appears to be 2 > 8 > 1. Two mechanisms are postulated to explain the transformation. One involves an endo-3,2-methyl shift and the other involves a circuitous route of an exo-3,2-methyl shift and several Wagner-Meerwein and 6,2hydride shifts. A preparation of 4-methyl-10-isobornyl sultone (18) from either camphor or fenchone is described. Sultone 18 rearranges to an endo sultone (29) at moderate temperatures, but the only product found at higher temperatures is an aromatic hydrocarbon, 3,4-dimethylcumene (35). Mechanisms are proposed to account for the aromatization reaction.A few years ago we discovered a unique thermal rearrangement of a sultone.1 Upon being heated to its melting point, 10-isobornyl sultone (1) rearranges to ezo-camphene sultone (2). It was subsequently found that solid 1 can be transformed to solid 2 at temperatures below the melting point of 1.Two mechanisms can be envisioned to explain the transformation: (A) an exo-3,2-methyl shift involving several steps or (B) an endo-3,2-methyl shift involving only a couple of simple steps. These mechanisms are