PTSA-systems

New military technology for collective filtration is focusing on PTSA-systems (Pressure and Temperature Swing Adsorption). Basically these use two filters alternatively, one providing protection while the other one is being cleaned , i.e. the toxic compounds desorbed by a combined action of reduced pressure and temperature. Due to the nature of the adsorption processes, this is very difficult to achieve with activated carbon filters as changing temperature and pressure will reverse physical adsorption, but will have a negligible effect on chemisorption (see section 4). 

The cyclobutanone ring in the ether 7, derived by ring expansion of an oxaspiropentane, intramolecularly alkylates the activated aromatic system on treatment with PTSA, leading to 2W-cyclobuta[c]chroman-4-ols 8 (X = OH). Subsequent fission of the four-membered ring yields 3,4-disubstituted 2//-chromenes <02SL796>. A variation of this approach allows the synthesis of the 4P-phenylsulfanyl derivative of 8 (X = SPh), oxidation of which affords the cyclopropa[c]chroman entity <02OL2565>. 

This work was expanded towards a classification of drug molecules into the established biopharma-ceutical classification system (BCS) on the basis of PTSA descriptors alone, which included separate models for solubility and permeability (Bergstrom et al. 2003). The PLS models reported for solubility and permeability resulted in a correct biopharma-ceutical classification for as many as 85% of the studied compounds, while an external FDA standard drug test set was correctly classified with 77 % accuracy. 

Treatment of Ar-tosyl azonane-3,8-dione 16 with PTSA resulted in an intramolecular aldol reaction giving tetrahydro-cyclopenta[r]pyridinone ring system 128 (Equation 3) <1995J(P1)1137>. 

As a consequence of the mild reaction conditions in the sequence to 3-halo furans 55 the palladium catalyst should be still intact to trigger another Pd-catalyzed coupling in the sense of a sequentially Pd-catalyzed process [31]. As a consequence, a sequential Sonogashira-deprotection-addition-cyclocondensation-Suzuki reaction, where the same catalyst system is applied in two consecutive significantly different cross-coupling reactions in the same reaction vessel should be feasible. Therefore, upon consecutive reactions of (hetero)aroyl chlorides 7 and THP-protected propargyl alcohols 54, Nal and PTSA, and finally, addition of 1.05 equiv of boronic acids 60 and sodium carbonate, the substituted 3-aryl furans 61 can be obtained in decent yields (Scheme 35). 

Kolbe conditions to give 914. Reduction with lithium aluminum hydride, acetonide formation (acetone, PTSA), and Collins oxidation furnishes aldehyde 915. A Homer—Emmons-type condensation of 915 with dienyl phosphonate 916 affords triene 917 in 50% yield. A Diels-Alder cycloaddition of 917 with L-phenylalanine-derived pyrrolone 918 (xylene, 170 °C, 4 days) produces a separable 4 1 mixture of 919 and the undesired regioisomer. Introduction of the methanol functionality and elaboration of the terminal isopropylidene group to a ra 5-a,j -unsaturated system completes the synthesis (Scheme 135) [203]. 

Another interesting feature of Bowden s system is its ability to act as an active membrane to carry out functional group-selective reactions. The PDMS matrix is hydrophobic, which allows organic molecules to diffuse in, but prevents ionic substances from doing so. In two separate experiments shown in Scheme 5.11, incorporated catalyst 4 was added to a mixture of methanol and water (90 10) containing two different diene substrates (135-136) that readily undergo RCM. In the first reaction, sodium hydroxide was added to deprotonate substrate 135, while in the second, /)-toluenesulfonic acid (PTSA) was added to help facilitate the diffusion of 135 into the PDMS matrix. Under the basic conditions of the first reaction, no formation of 137 was observed, whereas substrate 136 reacted to... 

It is advisable to include some carboxy functionality also as the cure reaction between acrylic and melamine resins is acid catalysed. In the more sophisticated industrial markets for acrylics, stoving temperatures are well controlled and adequate cure cycles are achievable. However, in the competitive general metal finishing market, low temperatures and short times are common, so whilst it is possible to externally catalyse using PTSA (para toluene sulphonic acid), this polar material remains in the film after curing to act as a pathway for water. Blistering on exposure to humidity is a common problem in acrylic-melamine systems which have been catalysed by sulphonic acids. 

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