Inclusion complex/crystal

Even for the oxoamides which do not form chiral crystals, enantioselective photoconversion to optically active (3-lactams can easily be accomplished by photoirradiation in their inclusion crystals with an optically active host compound. For example, irradiation of a 1 1 inclusion complex crystal of 9 with 11 [8] gave (-)-10 of 100% ee in a quantitative yield [9], The host compound 11 is recovered and can be used again. The chiral arrangement of 9 molecules in the inclusion complex was studied by x-ray analysis [9], A schematic stereoview of the inclu-... 

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 active oxazolidinones (91a-91d) of 95-100% ee were obtained by irradiation of the 1 1 inclusion complex crystals of nitrones (90a-90d) and optically active host compound 11 in the solid state in the chemical and optical yields indicated (Table 10) [48],... 

Enantioselective photoreactions in the solid state have many advantages as described in Section I. As reviewed in this chapter, highly enantioselective photoreactions can be accomplished in the solid state without using any chiral source. There are hopeful possibilities to find many other examples of similar absolute asymmetric photosynthesis in the solid state. Enantioselective photosynthesis in inclusion complex crystal with a chiral host compound will also be a new general method of asymmetric synthesis in future. By successful designing of many new chiral host compounds, the research field would also be developed widely. 

When chemical reactions are carried out in inclusion complexes, reactions can proceed selectively due to template control effects caused by the host compound. In some cases, reaction occurs only in the inclusion complex, but not in solution, since molecules can be arranged in the appropriate positions for reaction in an inclusion crystal. When an optically active host compound is used, enantiose-lective reactions can be accomplished. For some time we have been studying such selective reactions in inclusion complex crystals in the solid state. However, these reactions have already been published in the book Organic Solid State Reactions [1], In this present chapter, some representative topics and some recent new results of selective thermochemical and photochemical reactions in inclusion crystals are briefly summarized. 

A solution of chiral host and racemic guest compounds in an appropriate solvent is kept at room temperature until inclusion complex crystallizes out. In the complexation, it is necessary to use a solvent which does not form inclusion complex with the host compound. The inclusion complex formed is filtered and purified by recrystallization from solvent, if necessary. Host guest molar ratio is... 

In the optical resolution of bicyclo[2.2.1]heptanones (87a, 88-90), bicyclo[2.2.2]- octanones (91-94) and bicyclo[3.2.1]octanone (95) by complexation with various chiral host compounds, some best host-guest combinations were found. Resolutions of 88, 89, 90, and 92 were accomplished efficiently by complexation with 3 to give (+)-88 (100% ee, 33%), (-)-89 (100% ee, 16%), (+)-90 (100% ee, 60%), and (-)-92 (100% ee, 41%), respectively, in the optical and chemical yields indicated.36 However, resolutions of 93 and 95 were accomplished efficiently by complexation with 8a to give optically pure (-)-93 and (-)-95 in 56 and 48% yields, respectively. On the other hand, resolution of 94 can be accomplished only by complexation with 15c to give finally (-)-94 of 100% ee in 31% yield.36 Mechanism of these chiral recognition in the inclusion complex crystal has been studied by X-ray analysis.36 Nevertheless, none of 3,8a and 15c is applicable to the resolution... 

Pantolactone, dihydro-3-hydroxy-4//-dimethyl-2(3//)-furanone (103) which is an important starting material of the synthesis of pantothenic acid, was also easily resolved by complexation with 10a. When a solution of 10a (5.5 g, 9.93 mmol) and rac-103 (2.6 g, 20 mmol) in 1 1 benzene-hexane (20 ml) was kept at room temperature for 1 h, a 1 1 complex of 10a and (.S)-(-)- 03 was obtained, after two recrystallizations from 1 1 benzene-hexane, as colorless needles (2.05 g), which upon heating in vacuo gave (S)-(-)-103 of 99% ee (0.39 g, 30%).40 In order to clarify the mechanism of the precise chiral recognition between 10a and (S)-(-)-103, their inclusion complex crystal was studied by X-ray analysis40 and by AFM technique.41... 

Tanaka, K., Moriyama, A., and Toda, F. (1997) Novel Chiral Recognition in Host-Guest Inclusion Complexes Depending on Their Molar Ratios Efficient Resolution of 2,2 -Dihydroxy-1,1 -binaphthyl Derivatives and CD Spectral Study of Inclusion Complex Crystals, J. Org. Chem., 62, 1192-1193. 

When greater selectivity is required in the solid-state reaction, host-guest chemistry techniques can be applied efficaciously. Reaction in the solid state of the guest compound as its inclusion complex crystal with a chiral host can give an optically active reaction product. Various host compounds have been designed by us to follow this simple principle. 

Section 2.3.4 deals with a seeding process in the solid state. Racemic 2,2 -dihydroxy-1,T-binaphthyl forms two different kinds of inclusion complex crystals with ether in the host guest ratio, namely, 3 1 and 1 2. Selective inclusion complexation by contact of the racemic host crystal with ether vapor in the solid state can be controlled by adding a seed crystal. 

Making Inclusion Complex Crystals by Mixing or Grinding Host and Guest Crystals... 

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