Synthesis of -trans

Suggest an efficient synthesis of trans 2 heptene from propyne... 

The discovery of junipal focused the attention of Sorensen, who had been investigating the occurrence of polyacetylenes in Com-positae, on the possibility that these acetylenes were accompanied by thiophenes. From Coreopsis grandiflora Hogg ex sweet, 2-phenyl 5-(1-propynyl) thiophene (240) was isolated and its structure confirmed by synthesis of the tetrahydro compound, 2-phenyl-5-n-propyl-thiophene. From the root of tansy, the cis and trans isomers of methyl 5-(l-propynyl)-2-thienylacrylate (241) have been isolated. The total synthesis of trans (241) was achieved by reacting junipal with methylcarbethoxy triphenylphosphonium bromide (Wittig reaction) Several monosubstituted thiophenes, (242), (243), and... 

Of course, the key limitation of the ylide-mediated methods discussed so far is the use of stoichiometric amounts of the chiral reagent. Building on their success with catalytic asymmetric ylide-mediated epoxidation (see Section 1.2.1.2), Aggarwal and co-workers have reported an aza version that provides a highly efficient catalytic asymmetric synthesis of trans-aziridines from imines and diazo compounds or the corresponding tosylhydrazone salts (Scheme 1.43) [68-70]. 

Scheme 8.12 Schematic representation of the oxiranyl anion strategy for the synthesis of trans-fused THPs.

For the synthesis of the complex natural product, the terminus six-membered ketone 55 had to be transformed into an oxepane ring. For this necessary transformation, the authors were attracted by the single-carbon homologation of a pyr-anone (a sort of ring-expansion) because, in prindple, it could be used in an iterative sense at any stage of the 6-endo cydization in their poly-TH P-based synthetic approach for the synthesis of trans-fused 6,7,6 (THP-oxepane-THP) and 6,7,7 (THP-oxepane-oxepane) ring systems [28]. Treatment of ketone 55 with TMSCHN2... 

A stereocontroUed synthesis of trans-2,5-diaryl dihydro- and tetrahydrofurans starting with the readily available lactol 55 was reported <96JCR(S)309, 96JCR(M)1746 see also 96TL63>. 

A neat stereoselective synthesis of trans-fused tetrahydropyrano[3,2-c][l]benzopyrans involves treating salicylaldehydes with alk-4-en-l-ols and triethyl orthoformate. The selectivity is attributed to steric repulsion in the endo transition state, the precursor of the cw-fused compound <96CL889>. 

This synthetic sequence for an olefin synthesis has been further developed by Kocienski who has shown that eliminative desulphonylations carried out on / -acyloxysulphones are remarkably stereoselective for the synthesis of trans-disubstituted-olefins. The method has wide applicability in that a-lithio phenyl sulphones are readily generated, and are readily coupled to aldehydes or ketones, to give j8-hydroxysulphones. The hydroxyl function of these is then esterified and the synthesis is completed by the reductive elimination with sodium amalgam. Kocienski has prepared two reviews that summarize his syntheses of a range of natural products - one of which is diumycinoP obtained... 

Figure 1.7. Synthesis of trans- and cA-RhCl(PR3)[T ,T -R2P0CH2P(CH20H)2].

The synthesis of transtactic structures is based on catalysts in which the transition metal belongs to the 3d block (Ti, Cr, V, Ni). Particular emphasis is devoted to the synthesis of trans butadiene/piperylene copolymers and to their blends with synthetic cis-l,4-polyisoprene, with the aim of increasing the "green strength" of the latter. 

An allyl samarocene catalyst, [(CMe2C5H4)2SmCl(C3H5)MgCl2(THF)4, was employed for the synthesis of trans-Vl-b-VCL copolymers and poly(fra s-isoprene-co-hex-l-ene)-fr-PCL terpolymers [111]. The copolymerizations... 

Figure 2. Synthesis of trans-7,8-dihydroxy-anti(and syn)-9,10-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (anti- and syn-BPDE) via Method I ( ,2 ). Reagents (i) NaBH, (ii) H+ (iii) AgOBz, I- (iv) NBS (v) DBN (vi) NaOMe (vii) DDQ (viii) m-CPBA (ix) DMSO, H20 (x) t-BuOK.

Synthesis of ( )-trans-6-[4,4-bis(4-fluorophenyl)-3-(1 -methyl- 1H-tetrazol-5-yl)-1 (E), 3-[2- uC]butadienyl-4-hydroxy-3,4,5,6-tetrahydro-2H-pyran-2-one... 

The conventional synthesis of trans-2,5-dialkyl phospholanes starting from a chiral 1,4-diol is shown in Scheme 24.1. Originally, these 1,4-diols were obtained via electrochemical Kolbe coupling of single enantiomer a-hydroxy adds [25], but this method proved to be commercially impracticable and has since been replaced by more viable biocatalytic routes [26]. Reaction of the chiral 1,4-diol with thionyl chloride followed by ruthenium-catalyzed oxidation with so-... 

Asymmetric Synthesis of trans-2-Aminocyclohexanecarboxylic Acid Derivatives from Pyrrolobenzodiazepine-5,11-diones. 

Allais C, Constantieux T, Rodriguez J (2009) Highly Efficient Synthesis of trans-beta, gamma-Unsaturated alpha-Keto Amides. Synthesis 2523-2530... 

Stereoselective synthesis of trans 4-chloro-2-substituted piperidines can be achieved by the reaction of epoxides and N-protected homoallyllic amines using BiCl3 as the Lewis acid catalyst (Fig. 3). This method furnishes very good generality with respect to various epoxides with a regioselectivity that favors the trans-... 

This procedure is representative of a general procedure, for the synthesis of trans-2-sulfony1oxaziridines previously reported on a small scale (Table I). trans-2-(Phenylsulfonyl)-3-(p-nitrophenyl)oxaziridine was prepared on a 0.16-molar scale in greater than 85% yield. The Baeyer-Vill iger-type oxidation of the sulfonimine affords only the trans-oxaziridine. The synthesis of the sulfonimine (PhS02N=CHPh) directly from the sulfonamide and... 

The chiral (E)-oxazolone derived from 1,2-O-isopropyIidene-D-glyceraldehyde has also been used as a dienophile in the Diels-Alder reaction and, in this case, ( /Z) isomerization of the oxazolone can be avoided using heterogeneous catalysts that promote the synthesis of trans-adducts. ... 

A useful method for the diastereoselective and enantioselective synthesis of trans-and m-l,2-disubstituted cycloalkanecarboxaldehydes was devised by Koga et al.1990 starting from cycloalkanecarboxaldehydes. (S)-/er/.-Leucine ter/.-butyl ester, a highly effective chiral auxiliary reagent, could be recovered for recycling without any loss of optical purity in a reaction sequence similar to that in the acyclic synthesis of (202). 

Vic-diols can thus be easily converted to alkenes through their reaction with A, A -thiocarbonyldimidazule. The reported synthesis of trans-cyclooctene is illustrative of the method [219]. It should be noted that continuous elimination of rrans-cyclooctene by a stream of argon was necessary to avoid isomerization to the cis isomer. The conversion of cis-cyclooctene to ww-cyclooctene through a trithiocarbonate is described in the same paper. 

This reaction provides a synthesis of trans-calamene (7) from the ketene dithioacetal (5) of /-menthone. 

C=0 -> >C=CJV In a synthesis of trans-y-irone (4) the methylenation of 1 was carried out in two steps by conversion to the oxide 2 with dimethylsulfonium methylide followed by deoxygenation with TiCl4-LiAlH4 (1 1) and N(C2H5)3. 

Lin, J.M., Fay, L.B., Welti, D.H., and Blank, 1.1999. Synthesis of trans-4,5-epoxy-(E)-2-decenal and its deuterated analog used for the development of a sensitive and selective quantification method based on isotope dilution assay with negative chemical ionization. Lipids 34 1117-1126. 

Akzo has been instrumental in developing a new process for the stereospecific synthesis of trans- 1,4-cyclohexane diisocyanate [7517-76-2] (21). This process, based on the conversion of polyethylene terephthalate) [25038-59-9], circumvents the elaborate fractional crystallization procedures required for the existing -phenylenediamine [108-45-2] approaches. The synthesis starts with polyethylene terephthalate) (PET) (32) or phthalic acid, which is converted to the dimethyl ester and hydrogenated to yield the cyclohexane-based diester (33). Subsequent reaction of the ester with ammonia provides the... 

On the other hand, the addition of a quaternary ammonium salt to the reaction medium accelerates the isomerization of the radical intermediate [36]. Thus, the epoxidation of c/j-stilbene in the presence of A -benzylquinine salt gives rranr-stilbene oxide with 90% ee as major product (Table 6B.1, entry 24). This protocol provides an effective method for the synthesis of trans-epoxides. In contrast to the epoxidation of c/s-di- and tri-substituted olefins for which complexes 11-13 are the catalysts of choice, the best catalyst for the epoxidation of tetra-substituted conjugated olefins varies with substrates (Table 6B.1, entries 27 and 28) [37]. The asymmetric epoxidation of 6-bromo-2,2,3,4-tetramethylchromene is well-promoted by complex 14 and that of 2-methyl-3-phenylindene, by complex 12a. 

Scheme 30 Stereoselective synthesis of trans 3-amino-4-alkylazetidin-2-ones...

Scheme 80 Lewis acid-catalyzed synthesis of trans-P-lactams...

Other metal-amides, such as TiCp(NMe2)3, W2(NMe2)s and W(NMe2)s [77b], or EtZn(NPh2) and Et2Al(NPh2) [77c], have also been used in the synthesis of trans-2-hydroxycyclohexyl N,N-disubstituted carbamates through the same route. 

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