Dendralenes first synthesis

Scheme 1.48 The first synthesis of [4]dendralene, by Bailey and Nielsen, has no C-C bond forming events [217].

Skattebol and coworkers reported the first synthesis of 2,4-monocychc[4]dendralene 139 (dubbed DVC after its lUPAC name 2,3-divinyl-1,3-cyclohexadiene) over three publications between 1963 and 1965 [38-40]. Its synthesis was recently revisited, and DTDA chemistry studied by Sherburn and coworkers (Scheme 12.30) [41]. In stark contrast to the parent [4]dendralene (14), DVC... 

The double alkenylation approach (Scheme 1.1) has only been exploited relatively recently, most probably because of the rise to prominence of cross-coupling methodologies in recent times. The first double cross-couplings between 1,1-dihaloalkenes and metalloalkenes were isolated examples appearing in 1998 [9] and 2000 [10]. In 2002, Oh and Lim [11] reported a series of double Suzuki-Miyaura reactions between a 1,1-dibromoalkene 6 and alkenyl boronic acids 7 (Scheme 1.2). In 2007 and 2008, the Sherburn research group reported syntheses of substituted [3] dendralenes [12] and the state-of-the-art synthesis of [5]dendralene [13] respectively, transforming a 1,1-dihaloalkene via double... 

The first example of a dendralene synthesis via C3-C3 bond formation (Scheme 1.37) dates back to 1904, when Fellenberg reported an addition/elimination sequence between methyl magnesium bromide (224) and phorone (223) (Scheme... 

Electrocyclization reactions are powerful synthetic tools to prepare compounds of great molecular diversity. These reactions allow for the formation of many substituted cyclic and polycychc compounds important in medicine, materials science, cosmetics, and so on. The well-established mechanisms and predictable outcomes of electrocyclization reactions permit the elaboration of logical blueprints for the synthesis of important molecules. Among these, the Nazarov cyclization is a salient member of the family. Reported first in 1941 by Ivan Nikolaevich Nazarov [1], this reaction has been studied extensively and many variations and applications have been developed over the years. In this chapter, we will present selected examples highlighting the versatility and synthetic power of this transformation [2]. In its simplest form, the Nazarov employs a divinyl ketone as the starting material, a cross-conjugated compound which can be regarded as a 3 -oxa-[3]dendralene. 

The first successful natural product synthesis incorporating a DTDA reaction sequence was published by Sherburn and coworkers in 2008, and constitutes a formal synthesis of triptolide (165) (Scheme 12.34) [46]. The carbon framework of this natural product was rapidly assembled from silyl protected [3]dendralene 161, beginning with a DA reaction between the free alcohol and methyl acrylate. In situ lactonization provided semicyclic diene 162, which was subjected to a high-pressure DA reaction with quinone 163. Tetracycle 164 was functionalized further to intercept an intermediate from Berchtold s 1982 total synthesis of triptolide [47]. 

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