Heptenal precursor

Substituted TMM complexes also cycloadd to aldehydes in the presence of a tin cocatalyst such as MesSnOAc and MesSnOTs [31]. Reaction of 2-heptenal with methyl precursor (6) gave a mixture of methylenetetrahydrofurans (68) and (69). This regioselectivity is reversed with 10-undecenal and methyl precursor (5), where adduct (70) now predominates over (71). As in the carbocyclic system, the phenylthio group also functions as a regiocontrol element in reaction with cyclohexyl aldehyde. The initially formed adduct (72) eliminates the element of thio-phenol on attempted allyl rearrangement, and the overall process becomes a cycloaddition approach to furans (Scheme 2.21) [20]. 

With the growing interest for the polynorbomene, photoresist polymer, and cyclic olefin copolymer, the synthesis norbornene or bicyclo[2,2,l]-2-heptene (NBN) has drawn significant attention because it is one of the most important precursor for these materials. Norbornene is produced by the reaction between ethylene and cyclopentadiene (CPD) via the Diels-Alder condensation process at elevated temperature and pressure [1,2]. 

Thus, 4,5-benzo-3-thiatricyclo[4.1.0.02 7]heptene (46), which is regarded as a valence isomer of benzo[8]thiepin (4), appears to be an attractive precursor to 4. The most obvious method for the synthesis of 46 would be the application of the elegant Katz method 37> to the benzvalene synthesis. The well established success of the preparation of 43 36) by the Katz method makes this a likely route to 46. 

Evidence for de novo synthesis of pheromone components was obtained by showing that labeled acetate and mevalonate were incorporated into ipsdienol by male Ips pini [103,104]. Similarly, labeled acetate and other labeled intermediates were shown to be incorporated into frontalin in a number of Dendroctonus species [105]. Possible precursors to frontalin include 6-methyl-6-hep-ten-2-one, which was incorporated into frontalin by D. ruffipennis [106]. The precursor 6-methyl-6-hepten-2-one also was shown to be converted to bre-vicomin in the bark beetle, Dendroctonus ponderosae [107]. In addition, the expression patterns of HMG-CoA reductase and HMG-CoA synthase are tightly correlated with frontalin production in Dendroctonus jeffreyi [108, 109]. A geranyl diphosphate synthase cDNA from I. pini was also isolated, functionally expressed, and modeled [110]. These data indicate that the de novo isoprenoid biosynthetic pathway is present in bark beetles. A variety of other monoterpene alcohols such as myrcenol, pityol, and sulcitol are probably synthesized through similar pathways [111]... 

In the same vein is the observation that the lifetime of dipropylcarbene (59) in CH2C12 or cyclohexane is 0.3 ns,84 which, after statistical correction is 48 times less than the lifetime ( 21 ns) of Me2C in pentane.22 This reflects promotion by the propyl bystander groups of 59 of the 1,2-H shift to Z- and E-3-heptene.84 (Dipropylcarbene can be photolytically generated from either an oxadiazoline (diazoalkane)84 or diazirine85 precursor, but RIES lowers the efficiency of carbene production in either case.) Recently reported LFP lifetimes for Et2C and MeCEt in cyclohexane or benzene are 0.6-3 ns (cyclohexane) or 1-5 ns (benzene),14 in accord with the lifetimes of S822 and S9.84 The rate constants for carbene disappearance in cyclohexane ( 3 x 108 to 2 x 109 s 1) are presumably limited by 1,2-H shifts.14... 

J 0.2 Secondary Phosphines or Phosphites as Supramolecular Ligands 259 Table 10.1 Hydroformylation of 1-heptene with Pt(cod)2 as precursor and SPOs"... 

Methyl-5-hepten-2-one is a valuable precursor for microbial epoxidations and hence the production of chiral ethers with high optical purities. The biotransformation of 6-methyl-5-hepten-2-one (33) by Botryodiplodia malorum CBS 13450 to (/ )-sulcatol (84) was described [61], which is then epoxidised to the (55)-epoxide (85) and opened intramolecularly to cis-(2R,5R)-2-(2 -hydroxyisopropyl)-5-methyltetra-hydrofuran (86) and c/s-(35,67 )-3-hydroxy-2,2,6-trimethyltetrahydropyran (87). Reduction of 6-methyl-5-hepten-2-one (33) with baker s yeast to (5)-sulcatol (88) which was used as substrate for Kloeckera corticis... 

An alternative ester synthesis, the reaction of a carboxylate anion with an alkyl halide, was used by Madejewski [62] for the preparation of ( , )-l,9-dioxacy-clohexadeca-3,1 l-dien-2,10-dione (76) under dilution conditions. This 16-membe-red dilactone represents a precursor for the synthetic norpyrenophorin 77 a, the physiological activity of which corresponds to the one of the natural products pyrenophorin 77b and vermiculin 77c. The lactone 76 can be obtained in 77% yield by dimerization of ( )-7-bromo-2-heptenic acid (75) in DMF in the presence of potassium carbonate. 

The thermal, photochemical and Lewis acid catalysed dissociations of di-azabicyclo[2.2.1]heptenes with side chains of various lengths terminated by aldehyde groups 143 have also been examined [119] (Scheme 31). The course of the reaction depended on the length of the tether. For the precursor with n = 1, tetrahydroindenol 144 was the main isolated product. Thermolysis of... 

There are few cycloadditions involving either three alkenes, to produce cyclohexanes, or two alkenes and an alkyne, to produce cyclohexenes. ° The appropriate metallacyclic precursors containing the CpCo fragment have in fact been prepared and examined for reactivity. Both cobaltacycloheptanes and cobalt-acycloheptenes undergo -hy(Mde elimination, producing 1-heptenes and 1,6-heptadienes respectively, in preference to reductive elimination of the met and coupling to produce cyclic products. ... 

Thionophosphenous Acid Esters and Amides. Another ring system that we have found (75) to serve as a precursor of low-coordination species is the 7-phosphabicyclo[2.2.1]heptene system (also known as 7-phosphanorbomene). We have used this sytem for the thermal generation of derivatives of two previously unknown 2-coordinate species, the thionophosphenous amides 12 and the thionophosphenites 13 (Scheme 3). These species are trapped by a cycloaddition reaction with a diene to form the 5-membered 3-phospholene ring, as shown for 12. 

The yield data in Figures 3 and 4 can be rationalized on similar grounds. In the cis case the initial olefin-ozone adduct can be diverted to 3-heptene ozonide by butyraldehyde, and by doing so can eliminate a precursor to 3-hexene ozonide. This process continues to operate throughout a wide range of aldehyde concentrations with the total ozonide... 

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