Linear Production

Regarding AH, one bond is broken and a similar bond is formed in a linear product. The linear molecule is unstrained, but the magnitude of the strain relief upon ring opening depends on the ring size. 

A.luminum Jilkyl Chain Growth. Ethyl, Chevron, and Mitsubishi Chemical manufacture higher, linear alpha olefins from ethylene via chain growth on triethyl aluminum (15). The linear products are then used as oxo feedstock for both plasticizer and detergent range alcohols and because the feedstocks are linear, the linearity of the alcohol product, which has an entirely odd number of carbons, is a function of the oxo process employed. Alcohols are manufactured from this type of olefin by Sterling, Exxon, ICI, BASE, Oxochemie, and Mitsubishi Chemical. 

Unlike the 2-aLkyl-2-imida2olines, this stmcture is stable and resistant to hydrolysis. After ring cleavage, reaction with sodium chloroacetate yields linear products ... 

Cyclocondensation reactions starting from two components are possible only when both of them have two reactive centers An initial electrophilic-nucleophilic interaction yielding a linear product is followed by a second electrophilic-nucleo-... 

The rationale for the predominance of linear cyclization products versus angular cyclization products has been accepted as qualitative." The mechanism of the Combes reaction has been argued. It was initially proposed that cyclization to linear products was due to initial protonation of a more reactive site on the aromatic ring (1-position of 13 corrresponding to the 10-position of 15) thus, blocking cyclization to angular products. Bom showed this not to be the case for the cyclization of 2-naphthyl amino-2-penten-4-one. No 10-deutero material was observed. 

Benzoxazol-4-fluoro-aniline 77 and benzthiazol-aniline 80 both provided the linear product in very good overall yield. This was considered to be the normal or... 

In contrast to phthalocyanines (tetra- or octasubstituted) in which the isoindoline units carry all the same substituents, reports of phthalocyanines with lower symmetry, which have been prepared by using two different phthalonitriles, have rarely appeared. This is due to the problems which are associated with their preparation and separation. For the preparation of unsymmetrical phthalocyanines with two different isoindoline units four methods are known the polymer support route,300 " 303 via enlargement of subphthalocyanines,304 " 308 via reaction ofl,3,3-trichloroisoindoline and isoindolinediimine309,310 and the statistical condensation followed by a separation of the products.111,311 319 Using the first two methods, only one product, formed by three identical and one other isoindoline unit, should be produced. The third method can be used to prepare a linear product with D2h symmetry formed by two identical isoindoline units. For the synthesis of the other type of unsymmetrical phthalocyanine the method of statistical condensation must be chosen. In such a condensation of two phthalonitriles the formation of six different phthalocyanines320 is possible. 

These observations were explained in terms of an SE reaction between the 2-butenyl-(tributyl)stannane and tin(IV) chloride, which competes with Lewis acid catalyzed carbonyl attack. The 1 -methyl-2-propenyltin trichloride so formed reacts with the aldehyde to give linear products, or isomerizes to give the more stable ( )- and (Z)-2-butenyltin trichlorides which then react74. Similar results were obtained with titanium(lV) chloride, except that the anti-ad-duct was the major product from the butenyltitanium intermediate74. 

Scheme 23 Decarboxylative allylic elherification (1 = linear product, b = branched product) [69]...

As a mechanistic hypothesis, the authors assumed a reduction of the Fe(+2) by magnesium and subsequent coordination of the substrates, followed by oxidative coupling to form alkyl allyl complex 112a. A ti—c rearrangement, followed by a syn p-hydride elimination and reductive elimination, yields the linear product 114 with the 1,2-disubstituted ( )-double bond (Scheme 29). This hypothesis has been supported by deuterium labeling experiments, whereas the influence of the ligand on the regioselectivity still remains unclear. 

The condensation of amino acids likewise may produce cyclic and/or linear products the same is true of virtually all polyfunctional condensation reactions. The conversion of cyclic monomers and dimers (or other cyclic low polymers) to chain polymers was discussed in the preceding chapter the reverse reaction may often occur as well. Thus the alternative ring and chain products which may be produced by condensation of a bifunctional monomer usually are interconvertible, but with varying degrees of facility. 

The authors optimised conditions for the general reaction of 1,1-diphenylethylene and piperidine (Scheme 9.5). They obtained the highest TOF (288 h" ) and all linear product for this specific reaction when using complex 31 and 5 1 H iCO at 125°C for 24 h. An important note here is that the sterics of the substrate, 1,1-diarylethyl-enes, are responsible for generation of only linear products instead of the catalyst. With a one-pot method, the authors procured the active pharmaceuticals prozapine, fendilline, milverine, and diisopromine in 85%, 91%, 35% and 88% yield, respectively. The catalyst activities compare well to the established Rh-Xantphos system [33]. 

The percentage of linear product increases greatly by replacing CO with the much bulkier phosphine ligands. Due to the increased steric hindrance the catalyst shows a distinct preference for the n- over the tw-isomer. Tkatchenko (1991) has reported a detailed analysis of this system in terms of the correlation between catalyst performance (activity and selectivity) and detailed structure. 

Bis(diamino)alanes (R2N)2A1H were used for the hydroalumination of terminal and internal alkenes [18, 19]. TiCb and CpjTiCb are suitable catalysts for these reactions, whereas CpjZrCb exhibits low catalytic activity. The hydroaluminations are carried out in benzene or THF soluhon at elevated temperatures (60°C). Internal linear cis- and trans-alkenes are converted into n-alkylalanes via an isomerization process. Cycloalkenes give only moderate yields tri- and tetrasubstituted double bonds are inert. Hydroaluminahon of conjugated dienes like butadiene and 1,3-hexa-diene proceeds with only poor selechvity. The structure of the hydroaluminahon product of 1,5-hexadiene depends on the solvent used. While in benzene cyclization is observed, the reaction carried out in THF yields linear products (Scheme 2-10). 

The traditional and most extensively used method of synthesis of chlorocyclophosphazenes [NPCl2] involves the reaction of finely ground ammonium chloride with phosphorus pentachloride in a high boiling solvent such as sym-tetrachloroethane. This reaction affords a mixture of cyclic and linear products from which the individual products have to be separated, usually by fractional distillation in high vacuum (1, 5,17,18,35-39), (Eq. 1) ... 

Much progress has been made on regioselective hydroformylation of terminal alkenes in favor of the linear product. In particular bidentate phosphine or phosphite ligands, which have a natural bite angle 9 of about 110°, will favor the linear product. The most successful ligand types are BISBI [49, 50], BIPHEPHOS [51,52], and XANTPHOS systems (Scheme 8) [53]. 

Linear and angular thiazolothienopyridines have been synthesized from the thiazolopyridinethione 105, by reaction with bromoacetophenone 106 to give the linear product 107, or sulfur and triethylamine to give the angular fused tricycle 104 (Scheme 7) <2003JCCS1061>. 

To produce 100 000 tonnes of nonanal per year (25% down time, 100% conversion of substrate, 80% selectivity to nonanal) requires a production rate from the reactors of 19 tonne h 1, so that each batch must be 6.3 tonnes. Assuming a 1 1 ratio by volume of fluorous solventdiquid substrate and a 75 % loading, each reactor must have a volume of 20 m3. If the distillation column were fully integrated into the system it would be required to handle 19 tonnes aldehyde h 1. An increase in selectivity to the linear product, which could be achieved using careful ligand design would reduce the reactor size by up to 25%. 

C02 solubility. For example, the desired branched aldehyde formed upon hydroformylation of vinylnaphthalene is considerably more soluble in scC02 than its linear isomer. Therefore, the ratio of the branched to linear product increases from approximately 90 10 in the condensed phase to up to 98 2 in the C02 phase in a single extraction step under the low density conditions of catalyst separation. 

In addition to the increased proportion of linear product, other differences from the unmodified cobalt-catalyzed reaction may be noted. The... 

Another significant and positive characteristic of phosphine-modified cobalt systems is that a high proportion of linear products can be obtained from internal olefins, with only a small sacrifice in reaction rates (58), as shown in Table X. 

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