Diynes acyclic—

The subsequent chain extension can be accomplished by the pedestrian step-by-step homologation sequence via the acyclic diyne 12 or by a more efficient block-to-block strategy. The step-by-step approach includes protiodesilylation of diyne 12 followed by coupling with the propargyl chloride 9 following the same protocol as for the preparation of 12 from 11 and subsequent repetitions of protiodesilylation and alkylation with chloride 9 to reach stages 16 and 18, respectively (Scheme 3). 

The same type of bis-functionalization has been reported for the palladium-catalyzed borylstannylative carbocy-cyclization of 1,6-, 1,5-, 1,7-diynes, bis-propargylamine, and ether.377 It should be noted that even 1,2-dialkylidene cyclobutane can be obtained in reasonable yield. Ito has proposed the related silaborative reaction involving nickel(O) catalysis.378 This reaction has been performed in an intra- and intermolecular fashion. The intramolecular reaction allows the formation of cyclic dienes and the intermolecular process proceeds through a dimerization of alkynes to give acyclic dienes. 

Acyclic diperoxyketals, 14 287 18 457 Acyclic diyne metathesis (ADIMET), 26 951 Acyclic monoterpenes, aroma chemicals, 3 237... 

Bunz UHF (2003) In Grubbs RH (ed) Handbook of metathesis. WUey-VCH, 3 354-370 Acyclic diyne metathesis utilizing in situ transition metal catalysts an efficient access to alkyne-bridged polymers... 

An alternative method to make PAEs is the acyclic diyne metathesis (ADIMET) shown in Scheme 2. It is the reaction of a dipropynylarene with Mo(CO)6 and 4-chlorophenol or a similarly acidic phenol. The reaction is performed at elevated temperatures (130-150 °C) and works well for almost any hydrocarbon monomer. The reaction mixture probably forms a Schrock-type molybdenum carbyne intermediate as the active catalyst. Table 5 shows PAEs that have been prepared utilizing ADIMET with these in situ catalysts . Functional groups (with the exception of double bonds) are not well tolerated, but dialkyl PPEs are obtained with a high degree of polymerization. The progress in this field has been documented in several reviews (Table 1, entries 2-4). Recently, a second generation of ADIMET catalyst has been developed that allows... 

Scheme 2 Synthesis of PAEs by acyclic diyne metathesis (ADIMET).

Transition metal-catalyzed carbocycUzation reactions of tethered diene, enyne, diyne, and vinylallene derivatives represent an important class of transformations in synthetic organic chemistry. This may be attributed to the abihty to significantly increase molecular complexity through the highly selective combination of acyclic components, thereby facilitating the synthesis of complex polycychc products. Recently, rhodium-catalyzed carbocyclization reactions have attracted significant attention due to their immense synthetic versatility and the unique selectivities observed over a range of different transformations. This chapter provides an account of recent developments in rhodium-catalyzed [4-1-2] and [4-i-2-t2] carbocyclization reactions. 

The acyclic diyne metathesis polymerization of dodeca-2,10-diyne is catalysed by W(=CEt)(OCMe3)3 see equation 73. But-2-yne is eliminated and the product is an off-white insoluble powder with the same Tm as the polymer prepared from cyclooctyne (Section XII.B)7. 

This contribution describes the synthesis and properties of organic alkyne-bridged materials that have been made by alkyne metathesis or by Acyclic Diyne Metathesis (AD I MET). This review covers mostly poly(aryleneethynylene)s made at the author s laboratory in South Carolina. A comprehensive review covering poly(aryleneethynylene)s listing important contributions in adjacent areas has appeared [1, 2]. This chapter discusses the synthesis and properties of dialkyl-poly(paraphenyleneethynylene)s (dialkyl-PPEs) in relation to the concept of ADIMET with simple catalyst systems. 

PPEs by Acyclic Diyne Metathesis (ADIMET) Utilizing Schrock s Tungsten Carbyne Complex 11... 

On the other hand, most studies on twofold PKRs deal with the use of acyclic and cyclic diynes for the synthesis of phenyl or alkyl bridged ansa-zirconocenes such as 161. Scheme 47 shows an example of the reaction of a di-endiyne (159) that gives a twofold PKR, forming compound 160 [159,160]. 

Gleiter has studied the reaction of diynes with alkenes as an intermediate step in the synthesis of ansa-metallocenes 164. They have reacted acyclic diynes with ethylene [161] and cyclic diynes 162 in supercritical ethylene [162] giving tricyclic diketones 163 in low to moderate yields. The presence of coordinating heteroatoms in the link increased the reaction yields (Scheme 48) [163]. 

Acyclic Z 3-ene-l,5-diynes, such as 6, undergo the classical Bergman thermal cycloaromatization only at elevated temperatures (a photochemical promoted Bergman-type cycloaromatization of acyclic enediynes can take place under milder conditions on particular substrates). However,... 

Hexadehydro-[ 18]annulene 80>, 15, (see Table 4) possesses no inner protons and the six equivalent outer protons resonate at t 2.98. This represents a downfield shift of over 1 ppm from a model compound, cis-hex-3-ene-l,5-diyne, 9, (t 4.11). This model compound also served to clarify the interpretation of the singlet at t 5.55 in the case of l,5,9-tridehydro-[12]annulene, 1, a molecule for which aromaticity is not predicted. The downfield shift of 15 and the upfield shift of 1 from the acyclic model can then be attributed to a diamagnetic ring current in 15 and a paramagnetic ring current in 1. 

The symmetrical acyclic tetrayne 21 used as a precursor to these new pericyclynes was easily assembled by two different methods (Fig. 9-8) [22]. the lengthier of the two started with the familiar building block 8, whereas the shorter route relied on the more difficultly-accessible 3,3-dimethylpenta-l,4-diyne, 26. 

Stepwise preparations of the acyclic dimer and trimer of 3,3-dimethylpenta-l,4-diyne are outlined in Fig. 9-14 [22, 31]. These two compounds occupied pivotal positions in many of our synthetic routes to macrocycles containing 1,3-diyne units. 

Another type of alkyne polymerization, and one to which well-defined catalysts have been applied [67, 97], is the ring-closing polymerization of 1,6-diynes (Fig. 10-10). The resulting polymers are frequently soluble, and can be more highly conjugated than acyclic analogs because adjacent bonds are held closer to coplanarity by the ring. They are not expected to... 

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