Crystal structures reaction efficiency

The next landmark was the synthesis of the germylium, 22, and the stannylium ion, 23, by one-electron oxidations from the corresponding stable radicals with trityl TPFPB by Sekiguchi and co-workers. As in the case of the allyl cleavage to generate the mesityl-substituted cations, the reaction, in this case the oxidation, occurs at the periphery of the molecule and gives the possibility for efficient steric protection of the incipient cation. Both trivalent cations were obtained as their TPFBP salts and the crystal structure show well separated anions and cations. 

RuClj(Hcbx)(cbx) (Hcbx=A-2 -chlorophenyl-2-pyridine-carboxamide). This red-brown material is made from the ligand and RuClj, and its X-ray crystal structure determined (Fig. 1.36). The system RuCl2(Hcbx)(cbx)/Oj/M( butyraldehyde/DCE epoxidised a number of cyclic alkenes efficiently at room temperatures (Table 3.1). Addition of the radical trap 2,6-di-ferf-butyl-4-methylphenol stopped epoxidation reactions altogether, suggesting that a mechanism involving radicals is involved [801],... 

The tris and bis complexes of acetylacetone (2,4-pentanedione) (167) with chromium(III) have been known for many years (168,169).739 The tris compound is generally prepared by the reaction of an aqueous suspension of anhydrous chromium(III) chloride with acetylacetone, in the presence of urea.740 Recently a novel, efficient synthesis of tris(acetylacetonato)chromium-(III) from Cr03 in acetylacetone has been reported.741 The crystal structure of the tris complex has been determined.744 A large anisotropic motion was observed for one of the chelate rings, attributed to thermal motion, rather than a slight disorder in the molecular packing. 

Reaction of rac-1 -tert-buty l-3-chloroazetidin-2-one (28) with 25 gave the rac-phthalimide derivative (29). Optical resolution of rac-29 was accomplished efficiently by complexation with 15. When a solution of 15b and two molar equivalents of rac-29 in benzene-hexane (1 1) was kept at room temperature for 12 h, a crystalline 1 1 inclusion complex of 15b and (-)-29 was obtained. After one recrystallization from benzene-hexane, the crystals were chromatographed on silica gel to give pure complex consisting of (-)-29 of 100% ee in 63% yield. Decomposition of the complex with hydrazine gave optically pine (-)-3-amino- l-/m-butylazetidin-2-onc (30) in 44% yield.15 Mechanism of the precise chiral recognition between 15b and (-)-29 in their 1 1 complex was clarified by X-ray crystal structural analysis.15... 

Novel and efficient [2 - - 3] cycloaddition reactions of NADH analogues with Q derivatives rather than the hydride-transfer reactions occur in the presence of scandium triflate, Sc(OTf)3, in MeCN to afford the cycloadducts (142). When 1 -benzyl-4-tert-butyl-1,4-dihydronicotinamide (t-BuBNAH) is used as an NADH analogue in the Sc +-catalyzed reaction with Q, the crystal structure of the cycloadduct was determined successfully, as shown in Fig. 53 (142). 

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