Synthesis alkadienes

Allylic titanates having an electrofugal leaving group, e.g., trimethylsilyl68 75 - 77, at the 3-position are powerful reagents for the highly stereoselective synthesis of 1-hetero-substituted 3-alkadienes. For the carbonyl addition of the appropriate titanated allyl sulfides ( ) or carbamates ( and ), reliable y-selectivity and anti diastereoselectivity are reported. The... 

Tsuboi and coworkers20 reported a stereoselective synthesis of 3,5-alkadienic ester obtained from 2,4-dienoic isomers and their NMR data. 

It has been established that the course of the sequential pericyclic reaction of cyclopentadienones with acyclic conjugated alkadienes depends on the reaction temperature, thermal treatment at low temperatures affording 3a,4,7,7a-tetrahydroinden-l-one derivatives by way of a Cope rearrangement (see Scheme 38). Roman et al have developed an efficient stereoselective synthesis of enantiomerically pure i-nitrotricyclo[5.2.2.0 ]undeca-3,8-dienes via a tandem consecutive asymmetric Diels-Alder-Cope rearrangement (see Scheme 39). Adducts... 

POLYFUNCTIONAL COMPOUNDS. ALKADIENES. APPROACHES TO ORGANIC SYNTHESIS... 

Polyfunctional Compounds. Alkadienes. Approaches to Organic Synthesis... 

Miyaura, N. Yamada, K. Suginome, H. Suzuki, A. Novel and convenient method for the stereo- and regiospecific synthesis of conjugated alkadienes and alkenynes via the Pd-catalyzed cross-coupling reaction of 1-alkenyl-boranes with bromoalkenes and bromoalk-ynesj. Am. Chem. Soc. 1985, 107, 972-980. 

Polyunsaturated aliphatic alkohols, aldehydes, ketones, and esters occur as fragrance components in fats, oils, fruits and plants 158). As an example the synthesis of ethyl (2 ,4Z)-2,4-decadienoate (232, pear ester ), which is responsible for the aroma of bartlett pears 161) is given. 2,4-Diunsaturated ester 232 may be obtained by a number of highly stereoselective syntheses, a lot of them making use of the Wittig reaction. Ohloff and Pawlak condensed 4,5-epoxy-( )-2-pentenal 228 with the ylide generated from 229 (butyllithium/ether) to the alkadiene epoxide 230 which was oxidized with periodic acid to the 2,4-decadienal 231. 231 is subsequently converted with MnOj/NaCN in ethanol to the pear ester 232162) [75 % (Z)-amount of the C-4 double bond] (Scheme 44). 

Most recently, a new and general synthesis of conjugated alkadienes has been reported by the reaction of 1-alkenyldiorgarioboranes with 1-alkenyl halides in the presence of palladium catalysts and bases 142). According to this procedure, (Z, E)-alkadienes are readily obtained, as revealed in Eq, 84. 

Martin, M G G, Horton, D, Preparative synthesis of C-(a-D-glucopyranosyl)-alkenes and -alkadienes Diels-Alder reaction, Carbohydr. Res., 191, 223 - 229, 1989. 

---