Syntheses and X-ray structural investigations have been carried out for the two title compounds, C(20)H(16)N(2)O(2), (IIIa), and C(22)H(20)N(2)O(2), (IIIb). In (IIIa), the heterocyclic ring adopts a sofa conformation, while in (IIIb), the ring has a flattened boat conformation. In both molecules, the fused cyclohexenone ring adopts a sofa conformation. The dihedral angles between these two flat fragments are 3.5 (2) and 17.5 (2) degrees in (IIIa) and (IIIb), respectively. The dihedral angles between the pseudo-axial naphthalene substituents and the planes of the pyran rings are 90.9 (1) and 96.7 (1) degrees, respectively. In the crystal structure of (IIIa), intermolecular N-H.N and N-H...O hydrogen bonds link the molecules into infinite tapes along the b axis, while molecules of (IIIb) form centrosymmetric dimers via N-H...N hydrogen bonds, with only one H atom of the NH(2) donor group taking part in hydrogen bonding.

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Normal radical relay chlorination of cholestan-3 -ol directed by an attached m-iodobenzoate ester group affords a 9 -chloro steroid, but when the same reaction is conducted in the presence of an excess of CBr 4 the product is a 9 -bromo steroid. Similarly, when the same radical relay reaction is carried out in the presence of an excess of (SCN) 2 rather than CBr 4 , the product is a 9 -thiocyano steroid. Several other examples of these reactions have been developed. These tandem remote functionalization reactions succeed because an intramolecular hydrogen abstraction by a complexed-chlorine atom generates a specific substrate radical in each case.Some years ago the remote radical chlorination of steroids and of linear alkanols directed by attached templates was described. 1 These template-directed reactions differed from those of the traditional synthetic style as geometric constraints, rather than just intrinsic chemical reactivity, were a dominant factor in product formation. Furthermore, without template control a low yield of a complex product mixture would have resulted in each case. The novel steroid products were also of potential medicinal interest and would be difficult to prepare by the traditional synthetic approach. Therefore, it was of interest to generalize the remote chlorination chemistry to other functional groups. Recently the extension of this chemistry to the formation of carbon-bromine and carbon-sulfur bonds by tandem radical chain reactions on one substrate was communicated. 2 This report describes how general the latter reactions were with more of the previously developed 1 radical relay systems. Results and discussionA general strategy for introducing remote functional groups other than chlorine has been developed (Scheme 1). The template-complexed chlorine atom would be produced as in normal remote radical chlorination chemistry. In the first radical chain propagation step, an intramolecular HCl elimination reaction would take place. In the second step, an additive X᎐Y (X,Y ≠ Cl) would react with the substrate radical to give the functionalized product as well as a free radical that was capable of propagating the chain reaction. Implicit in this strategy was the necessity to identify additives which reacted with the substrate radical at a rate similar to that at which the chlorine sources did. This strategy towards remote functionalization was of the tandem type; one reagent was responsible for substrate radical formation, while a second was responsible for the substrate radical functionalization.The initial substrate chosen to test the tandem strategy was Scheme 1cholestan-3α-yl m-iodobenzoate 1 (Scheme 2). This ester was reported to afford 9α-chloride 2 upon reaction with phenyliodine dichloride (PID) under radical relay conditions (Scheme 3). 3 Chloride 2 was found to be a robust material at room temperature and treatment with base or Ag + was necessary to effect elimination. 3 The initial additive tried in the tandem scheme was Br 2 , since this material has long been known to react...

Intramolecular electron-transfer (ET) rates have been measured as functions of reaction driving force (0.0−2.0 eV) and temperature (200−280 K) for a series of iridium dimers (Ir2) covalently bound to substituted pyridinium (py+) groups. We found that the rates of recombination reactions (py• → Ir2 +) at high driving forces are strongly dependent on temperature and that Ir2* → py+ and py• → Ir2 + rates in both the normal and inverted regions are slower on deuteration of the pyridinium acceptors. Analysis of the rates in terms of semiclassical theory gives the following parameter values:  H AB = 52(9) cm-1, λ = 1.05(2) eV (280 K); H AB = 22(2) cm-1, λ = 1.04(1) eV (210 K). 4-Phenyl-N-ethylpyridinium iodide, chosen as a model for the acceptors in the Ir2* → py+ reactions, exhibited resonance Raman scattering that implicated a 1565-cm-1 mode as dominant for inner-sphere reorganization.