Monosubstituted alkenes, synthesis

Negishi et al. reported the regioselective synthesis of diisoalkyl derivatives from monosubstituted alkenes in yields ranging from 58-95%, Scheme 8, from the in situ prepared ethylene complex Cp2Zr(C2H4).35 The zirconocene-ethylene complex presumably undergoes alkene insertion to furnish a zirconacyclopentane which further reacts with diethylzinc to yield the diisoalkylzinc compound. 

Ganem, B. Hydrozirconation-transmetalation a mild, direct route to higher-order vinylic cuprates from monosubstituted alkenes. One-pot synthesis of protected prostaglandins from alkynes and cyclopentenones in situ generation of higher-order cyanocuprates from alkenylzirconium intermediates. Chemtracts Org. Chem. 1991, 4, 44-47. 

Even if the only difference between the two alkenes is the number of substituents, that can be enough for some reactions. If the substituents are simple alkyl or aryl groups, then the more highly substituted alkene will be the more nucleophilic. This is enough to allow the epoxidation of the trisubstituted alkene in citronellene2 28 while leaving the monosubstituted alkene intact and provide a source of the optically active acid 31 for Nicolaou s synthesis of rapamycin.3... 

We return to two compounds we made earlier by the AE reaction propranolol 7 and diltiazem 67. In both cases the synthesis is easier as we do not have to start with an allylic alcohol. The synthesis of propranolol41 uses the allyl ether 188 that gives the diol 189 with good ee in the AD reaction for a monosubstituted alkene. Transformation to the epoxide 190 shows no loss of ee. Reaction with /-Pi NIE was already known to give propranolol 7. This is a very short synthesis from easily made starting materials. 

The development of organoyttrium catalysts provided a major breakthrough in terms of efficiency and selectivity in the synthesis of organosilanes [35]. These catalysts reacted with monosubstituted alkenes and reactive disubstituted alkenes within hours at room temperature, providing high yields of the desired... 

Terminal alkenes, both mono- and disubstituted, have been prepared using the title reagent. In Wood s recently disclosed synthesis of welwitindolinone A isonitrile, he achieved a selective dehydration of the less hindered secondary alcohol in 32 to yield monosubstituted alkene 33. 13 Mori obtained terminal disubstituted alkene 35 in 93% yield from phosphorylated tertiary alcohol 34 in the penultimate step in his total synthesis of acoradiene (36), the aggregation pheromone of the broad-homed flour beetle.14... 

Domino metathesis of siloxy-tethered dienynes offers attractive opportunities for the synthesis of stereochemically defined 1,3-dienes after desilylation [21]. These reactions also allow the efficient preparation of highly substituted cycloolefins, which is illustrated in Scheme 2.43 [21b,c]. Selective double cydization of silaketal 118 via initiation at the monosubstituted alkene led to a fused 6/7-bicychc product which was subsequently desilylated to afford the triol 119 in high overall yield. 

The scope of the synthetic procedure to substituted 1,3-butadienes 16 was later broadened by the same group, with the report of 18 examples of the 1 1 1 coupling of iodoarenes, diarylacetylenes, and monosubstituted alkenes. The mixture Pd(OAc)j, LiQ, and NaHCOj led to the desired products in moderate yields, although minor amounts of the Mizoroki-Heck-type product (ArCH=CHR) were also formed [30]. For the synthesis of 1,3,5-hexatriene derivatives 17, a modification of the former procedure consisting of using silver acetate as a base leads to the 1 2 1 coupling of iodoarenes. 

The synthesis of 1,3,5-hexatrienes 18 by the palladium-catalyzed 1 1 1 coupling of p-bromostyrenes with internal alkynes and monosubstituted alkenes was also achieved (Scheme 3.15) [30b]. 

Very recently, Jiang et al. developed a palladium-catalyzed three-component coupling reaction for the synthesis of 1,3-butadienes that involves the sequential formation of a C(sp )—C(sp ) bond and a C(sp )- (sp ) bond from a benzyl chloride, a terminal alkyne, and a monosubstituted alkene [32],... 

Intramolecular insertion of simple alkenes is possible (Scheme 4.74). While this is potentially a powerful cyclization method, it has seen little application beyond a synthesis of aphidicolin 4.209 (Scheme 4.75)X and appears to be limited to a small group of alkenes, such as monosubstituted alkenes and cyclopentenes. ... 

In the course of a synthesis of (-)-P-conhydrine 33 (Tetrahedron Lett. 2008, 49, 6508), Nabin C. Barua of North East Institute of Science and Technology needed to reduce the nitro group of 31 to the amine without reducing the very reactive monosubstituted alkene. Zn/NH Cl served well. James C. Anderson of the University of Nottingham solved (J. Org. Chem. 2008, 73, 8033) a similar problem in a synthesis of (+)-6 -hydroxyarenarol 36. In that case, Raney Ni reduced the carbon-sulfur bond without affecting the monosubstituted alkene. 

With a-monosubstituted ylides the oxidation results in the formation of alkenes (by subsequent Wittig reaction on the intermediate aldehyde). A recent example of such synthesis is found in the preparation of all-(Z)-cyclododecate-traene by oxidation of the appropriate bis-ylide [33]. It must be pointed out that an approach of the same macrocycle based on ring closing metathesis was found ineffective. 

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