Photocyclization inclusion complex

Keywords nitrone, photocyclization, inclusion complex, oxaziridine... 

Enantiocontrol of the photocyclization of Ar-methyl-AT-phenyl-3-amino-2-cyclohexen-l-one (151a,b) to the corresponding AT-methylhexahydro-4-car-bazolones (153a,b) via the dipolar ionic intermediate (152a,b) (Scheme 22) was also accomplished by photoirradiation of 1 1 inclusion complexes of 151 a,b with the chiral hosts lOa-c. Of the complexes prepared, 10a-151a, 10a-151b,... 

Table 15 Enantioselective photocyclization of anilides and glyoylamide in their 1 1 inclusion complexes with 10b or 10c...

When 8 a is used instead of 2a for complexation with 50a, two kinds of 1 1 inclusion complexes 57 were obtained one (57a) is photoreactive and the other (57b) is photostable. Thus when a solution of 8a and an equimolar amount of 50a in benzene was kept at room temperature for 10 h, a 1 1 inclusion complex between both (57a) was obtained as colorless fine needles of mp 110 to 123 °C which upon irradiation in the solid state for 49 h gave (1 R,5S)-(+)-52a of 3.6% ee in 30% yield 13). However, recrystallization of 57a from benzene gave a different kind of 1 1 inclusion complex (57b) as colorless needles of mp 123-125 °C which is photostable. Photocyclization of 50a in 57b is probably prevented by a steric hindrance. The different behavior of 57a and 57b may be clarified in future by X-ray structural studies. 

Table 10. Solid-state photocyclization of oxoamides to p-lactams using inclusion complexation...

Enantioselective photocyclization of 74 occurred efficiently in the inclusion complex with 2a. In particular, the selectivity is very high in the case of 74a. However, control is inefficient in the 1 2 complex 85 composed of 2a and 74c. The host guest ratio probably depends on the packing of the components in the crystal. The packing is... 

The most successful enantiocontrol of photocyclization of a a-oxoamide to a P-lactam in an inclusion complex is represented by the photoreaction of the 1 1 complex... 

Cyclobutanol formation is not usually an efficient process for simple aliphatic ketones. It has, however, been shown12 that irradiation of the urea inclusion complex of 5-nonanone is more effective, providing l-butyl-2-methylcyclobutanol in 40% yield, with the balance of the ketone undergoing photochemical fragmentation. The cyclobutanol product is a 97 3 cisjtrans mixture. In the absence of urea, photolysis proceeds to give the cyclobutanol in 24% yield, as a 60 40 cisjtrans mixture. Photocyclization has also been improved by inclusion in zeolites13. 

Keywords A-alkylfuran-2-carboxanilide, inclusion complex, photocyclization, lactam... 

Optically active hosts 12 [10] and 13 [10] are also useful for an enantioselective photocyclization of 9 [11], The mechanism of the enantioselective reaction of 9 in an inclusion complex with 12 has also been studied by x-ray analysis [12],... 

B. Enantioselective Intramolecular Photocyclization Reactions of Achiral Molecules in Inclusion Complex With a Chiral Host Compound... 

Intramolecular [2 + 2] photocyclization reactions of 2- /V-(2-propcnyl)amino]cy-clohex-2-enones (67) are also controlled enantioselectively by carrying out irradiation in inclusion complex with a chiral host compound. When inclusion crystals of 67 with 12 are irradiated in the solid state, optically active 9-azatricyclo[5.2.1.0]-decan-2-ones (68) were obtained in the chemical and optical yields indicated in Table 3 [30],... 

Interestingly, the enantioselective conversion of 88a in the inclusion complex crystal with 12b into (+)-89 proceeds by a partial single-crystal to single crystal photocyclization manner [47],... 

Optically pure P-lactam derivatives can also be prepared by an enantioselective photocyclization reaction of 2-pyridone in its inclusion complex with a chiral host. For example, irradiation of the 1 1 inclusion complex of 1 and 4-methoxy-/V-inethyl-2-pyridone (33) in the solid state gave (—)-34 of 100% ee... 

The next example deals with the enantioselective photocyclization of a-tropolone alkyl ethers [182]. Cyclization occurs through an allowed 4e -disrotation that can result in opposite optical isomers depending on the direction of rotation (Sch. 37). Racemic products are obtained in solution, but irradiation of crystalline inclusion complexes of a-tropolone alkyl... 

Photocyclization of acrylanilide 21 to 3,4-dihydroquinolin-2(l//)-one 22 was applied in alkaloid synthesis, but enantiocontrol was unsuccessful in solution [46]. Solid-state photolysis of 21 in the 1 1 inclusion complexes with optically active host compounds 6a-c gave 22 in almost perfect optical yields (Scheme 5) [34,47]. X-ray crystallographic analysis revealed that the configuration of the photocyclization products depended on slightly different lattice structures, which were controlled by the host molecules. 

Table 15-22. Photocyclization reactions of 116 in 1 2 inclusion complex with 2 in a water suspension.

Photocyclization of 2-phenylthio-3,5,5-trimethylcyclohexen-I-one (118) to the dihydrobenzothiophene derivative (119) [71] can also be carried out enantioselec-tively. Photoirradiation of 118a-g in their inclusion complexes with 2c for 30 h in a water suspension gave (+)-119c (72% ee, 86% yield), (-i-)-119d (75% ee, 80% yield), (-l-)-119e (81% ee, 92% yield), (-r)-119f (70% ee, 89% yield) and (-(-)-119g (83% ee, 91% yield), respectively, in the optical and chemical yields indicated [72]. 

The photocyclization of acrylanilide (122) to 3,4-dihydroquinolinone (123), which was first reported in 1971 [74], can also be carried out enantioselectively by using a chiral host compound. Irradiation of the finely powdered 1 1 inclusion complex of 122 with 26 in a water suspension gave (-)-123 of 98% ee in 46% yield [75]. By the same procedure, optically active 125, 127 and 129 were prepared from 124, 126 and 128, respectively (Table 15-23) [75]. 

Table 15-23. Photocyclization of anilides in 1 1 inclusion complexes with 2b and 2c.

Table 2. -Lactams by photocyclization of a-ketoamicies ( inclusion complex with desoxycholic acid)...

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