Crystal of DMAP

A solution of 4 (110 mg, 0.26 mmol) in a mixture of dichloromethane (25 mL) and methanol (8 mL), cooled to —78°C, was ozonized until the solution turned blue (about 4 min). Excess ozone was removed by a stream of nitrogen, the solution was allowed to attain room temperature and was concentrated to dryness. The crude product was dissolved in THF (10 mL) and a borane-THF complex (1.04 mL of a -M solution) was added at room temperature under nitrogen. After 24 h the reaction mixture was treated with diluted hydrochloric acid (5 mL) and the solution was extracted with ethyl acetate (4x15 mL). The combined extracts were dried (MgS04) and concentrated to dryness. The residue was dissolved in dichloromethane (20 mL) and acetylated with acetic anhydride (62 p,L, 0.66 mmol), triethylamine (200 p,L, 1.50 mmol), and a crystal of DMAP, under nitrogen atmosphere. After 12 h the reaction mixture was concentrated under diminished pressure, and the crude product was purified on a silica gel column with hexane-ethyl acetate (3 1) to give 5 (73 mg, 65%) mp 103°-105°C (after crystallization from hexane), [a]D — 26.6° (c 0.7, CHC13). 

Initial studies on the reaction of dmap -> Al(Me2)Sb(SiMe3)2 63 with -Bu3A1 and -Bu3Ga resulted in the formation of the expected adducts dmap -> AlMe2Sb(SiMe3)2 M(f-Bu)3 (M = A1 82, Ga 83). Their solid state structures were determined by single crystal X-ray diffraction130 (Fig. 38). 

Recently, Oppolzer s group reported on the synthesis and use of a new sulfinylating agent,107 the /V-sulfinyl sultam 82, as part of a broad program on the use of the versatile bornane-10,2-sultam 81 in asymmetric synthesis.108 The condensation of p-TolSOCI with 81 in THF, using dimethylaminopyridine (DMAP) as catalyst, gave the /V-(p-tolylsulfinyl)bornane- 10,2-sultam as a 6.2 1 diastereomeric mixture. Crystallization of the mixture from E O/hexane afforded pure 82 in 77% yield. X-ray analysis showed the absolute configuration at the sulfinyl sulfur to be (/ ). The reaction has been shown to be kinetically controlled, in contrast to the results obtained when n-BuLi was used instead of DMAR In the latter case, the reaction was under thermodynamic control, in accord with the result obtained by Evans with iV-sulfinyl oxazolidinone (Scheme 25). 

To a solution of2 (340 mg, 0.9 mmol) inTHF (30 mL) cooled to -78°C K-Selectride (1.34 mL of a 1-M solution in THF) was slowly added (1 h) under nitrogen atmosphere. The reaction mixture was stirred for an additional 1 h, quenched with an aqueous saturated solution of NaHCOj (20 mL) and allowed to attain room temperature. The product was extracted with ethyl acetate (4 x 20 mL), the combined extracts were dried (MgS04) and concentrated to dryness. The residue was dissolved in dichloromethane (30 mL), then triethylamine (500 p.L, 3.6 mmol), acetic anhydride (250 pL, 2.6 mmol), and a crystal of A(A-dimethylaminopyridine (DMAP) were added, and the mixture was left under nitrogen at room temperature. After 24 h the solution was concentrated to dryness and the residue was chromatographed on a silica gel column with hexane-ethyl acetate (3 1) to give 25,35,4/J,6/ -3,4-diacetoxy-2-(l-menthyloxy)-6-(2-furyl)-tetrahydropyran 4 (290 mg, 79%) mp 127°-129°C, [a] - 5.3° (c 0.8, CHCy. 

An improved protocol for the efficient conversion of inosine into its 3 -phosphoramidite synthons for solid-phase oligonucleotide synthesis has been described. This procedure, which almost doubled the literature reported overall yields starting from inosine, was optimized for scale-up to multigram quantities. The portion-wise addition of DMT-Cl to a solution of inosine in DMSO and pyridine prevented multiple-site protections, which was also reported to occur in the presence of DMAP or triethylamine. Treatment with TBDMSCl in the presence of silver nitrate and pyridine in THF offered a mixture of the 2 - and 3 -substituted nucleosides from which the 5 -0-dimethoxytrityl-2 -0-tert-butyl-dimethylsilyl-protected inosine was crystallized in ethyl acetate. The mother liquor was enriched with the 2 -isomer by treatment with triethylamine in methanol. Standard conditions for phosphitylation were then applied to yield... 

Philip Anthony. S. Radhakrishnan. T.P. Perfectly polar assembly of moleeular dipoles in crystals of Zn(ll)(DMAP)-(acac)2—A case of self-poling. J. Chem. Soc.. Chem. Commun. 2001. 931. 

Typical procedure. o-(4-Nitrophenylene) carbonate (NPC) 721 [504] To a stirred solution of 4-nitrocatechol (3.10 g, 20 mmol) in THF (250 mL), a solution of DMAP (2.44 g, 20 mmol) in THF (100 mL) was added in a single portion. To this mixture, a solution of phosgene (for a safe source, see Chapter 7) (20% in toluene, 50 mL, 84 mmol) was added dropwise with stirring over a period of 2 h and the reaction mixture was stirred for a further 2 h at room temperature. A white precipitate began to form on addition of the phosgene solution. Nitrogen was bubbled through the suspension for 15 min and then the precipitate was removed by filtration. The filtrate was concentrated and the residue was crystallized from hexane to yield NPC 721 (1.49 g, 41%) as pale-yellow needles mp 100-101 °C. 

To provide one practical example of the complexity of the situation, proton transfer in the carboxylic acid-pyridine synthon has been investigated systematically by Tocher and co-workers through co-crystallisation of pyridine or 4-dimethylaminopyridine (DMAP) with five different carboxylic acids (Table 2.1) Since the pATa value for the conjugate acid of DMAP (pATa = 9.70) is considerably larger than that of any of the carboxylic acids, salts should be expected for all crystals containing DMAP and this was indeed found to be the case. However, two different crystal forms were established for the fumarate salt, both of which also contained neutral fumaric add molecules. 

The successful synthesis of the novel 2(S)-mercapto-Y-butyrolactone (19) is shown in Figure 7. This synthesis starts with 2(R)-hydroxy-Y-butyrolactone (16) which is conunercially available or may be conveniently prepared ftom d-malic acid 15). Conversion of 2(R)-hydroxy-Y-butyrolactone (16) to the corresponding crystalline 2(R)-mesylate 17, was accomplished by treatment with methanesulfonyl chloride in the presence of DMAP in EtOAc. The mesylate could be isolated by crystallization from the reaction mixture after work-up. Fortunately, a remarkable enantiomeric purification occurred during this... 

Single crystal X-ray analyses of 58-67 reveal the formation of monomeric R2ME(Tms)2 molecules, to which one dmap molecule is coordinated. 

Single crystal X-ray analyses clearly reveal the formation of monomeric, dmap-stabilized compounds. The most important bonding parameters of the alane and gallane derivatives are given in Table XXIII. 

To a stirred soln of a Fmoc-protected a-amino acid (32 mmol) and BzlSH (64 mmol) in anhyd THF (300 mL) at rt under argon were added DMAP (3.2 mmol) and DCC (35 mmol). The mixture was stirred overnight. The solvent was removed under reduced pressure, the residue was dissolved in EtOAc (400 mL) and washed with 1M HC1 (2 x 300 mL). The organic soln was dried (anhyd Na2S04), and filtration and removal of the solvent gave the crude product which was crystallized (Et20) to yield the pure 5-benzyl Fmoc-a-amino thioesters. 

Boc-(R,/ )-/ra s-ACHC-OBzl (31 0.047 g, 0.14 mmol) was dissolved in 4M HCl/dioxane (0.5 mL) and stirred for 1 h. The solvent was then removed under a stream of N2, and the residue 34 was dried under vacuum. Boc-(f ,f )-trans-ACHC-OH (33 0.034g, 0.14mmol) and DMAP (0.023g, 0.19mmol) were added followed by DMF (lmL). EDC (0.059 g, 0.31 mmol) was added, and the reaction was stirred for 48 h under N2. Solvent was removed under a stream of N2, and the residue was further dried under vacuum. To this residue was added 1M HQ ( 3mL) and the solid that did not dissolve was isolated by suction filtration and washed with additional 1M HC1. The solid was dried under vacuum yield 0.051 g (79%). Fluffy crystals were grown by vapor diffusion of heptane into a soln of 35 in 1,2-dichloroethane mp 195 °C. 

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