Domino Diels-Alder reactions. 6. Domino Diels-Alder cycloadditions to 9,10-dihydrofulvalene and 11,12-dihydrosesquifulvalene. A synthetic tool for the elaboration of polycondensed alicyclic systems

Abstract

The practicality of constructing highly condensed alicyclic frameworks through multiple Diels-Alder cycloaddition reactions (of the domino or pincer type) involving 9,10-dihydrofulvalene, decachloro-9,1O-dihydrofulvalene, and 1 I , 12-dihydrosesquifulvalene is presented in full detail. Illustrative of the synthetic potential of the method are efficient syntheses of hexahydro-3,4,7-methenocyclopenta[a]pentalene (lo), octahydro-3,6-dimethylenedicyclopenta[cd,g~]pentalene ( l l ) , triquinacene (12), and a number of previously unknown (CH)12 isomers. The greatly enhanced 4~ donor reactivity of cyclopentadiene relative to cycloheptatriene rings does not permit the isolation of intermediate stage adducts in those instances where only fivemembered cycles are involved. When the larger rings are present, temperatures in excess of 130 OC are required to complete the overall formation of four new (T bonds. Decachloro-9,10-dihydrofulvalene exhibits greatly reduced reactivity relative to its hydrocarbon analogue and consequently is of limited practical utility. The varied responses of four somewhat related polycyclic azo compounds (37,48,49, and 63) to thermal and photochemical activation are also demonstrated.Those structural features unique to the [2.2]-and [3.3]-paracyclophanes rather tightly compress transannularly disposed .rr networks and beget a modicum of interaction between them.4 Of particular relevance to the present investigation are those two-stage cycloadditions which lead to polycyclic products. There are formally two ways in which such multistage C-C bond forming reactions can occur. Illustrative of the first type are the efficient condensation of [2.2](2,5)furanophane(1) with tetrachlorocyclopropene to give 2,s the reaction of anti-[2.2]naphthalenophane (3) with singlet oxygen in methanol to provide 4,6 and the capture of dimethyl acetylenedicarboxylate by anthracenophane 5.' Here initial intermolecular cycloaddition of a dienophile to a 1,3-diene part structure generates a new olefinic center which subsequently becomes directly involved as a dienophile in a n ensuing intramolecular (rd + x2) bonding scheme.8 W e shall hereafter refer to such multiple cycloaddition processes as "domino Diels-Alder" reaction^.^ 2 -1 -* CH300C-Czc-COOCH~ &/ . & COOCH3 6 COOCH3 s The second cyclocondensation pathway requires that the dienophile be originally acetylenic and proceeds by utilization of both degrees of unsaturation in the triple bond to achieve two-stage cyclization. The reactivity of 1Io and naphthalenofuranophane SI1 toward dimethyl acetylenedicarboxylate serves as prototypical examples. Their classification as "pincer Diels-Alder reactions" would seem appropriate since this term clearly connotes that compression of a dienophile between two diene components has transpired. Either process is seen to lend itself readily to the formation of four new C-C bonds and to the construction of a rather elaborate polycyclic structure in a single laboratory manipulation. Clearly, if less sterically compressed polyolefins were...

Preparation and Reactivity of [D3d]‐Octahedrane: The Most Stable (CH)12 Hydrocarbon

“…Reduction of 4 with sodium in toluene in the presence of chlorotrimethylsilane according to the published procedure [10] yielded a mixture of endo,endo-, endo,exo-, and exo,exo-stereoisomers of diester 6 in a 75:13:2 ratio (80-91 % yield). Base-catalyzed isomerization in the presence of sodium methoxide [10] gave a mixture enriched with the exo,exo-diastereomer (ratio 1:21:67). The addition of bromine to 6 provided a mixture of dibromodiesters including 7 which, upon treatment with sodium methoxide, underwent twofold g-dehydrobromination to yield 8 (13-14 %).…”

“…[2,4] This is in line with the ease of selective adamantane functionalizations under ionic (bromination, nitroxylation) and free-radical (chlorination, hydroxylation) conditions. Herein we present and discuss the preparation, structural and energetic features as well as the reactivity of [D 3d ]-octaAbstract: The synthesis of the (CH) 12 hydrocarbon [D 3d ]-octahedrane (heptacyclo[6.4.0.0 2,4 .0 3,7 .0 5,12 .0 6,10 .0 9,11 ]dodecane) 1 and its selective functionalization retaining the hydrocarbon cage is described. The B3LYP/6-311+G* strain energy of 1 is 83.7 kcal mol À1 (4.7 kcal mol À1 per CÀC bond) which is significantly higher than that of the structurally related (CH) 16 [D 4d ]-decahedrane 2 (75.4 kcal mol À1 ; 3.1 kcal mol À1 per CÀC bond) and (CH) 20 [I h ]-dodecahedrane 3 (51.5 kcal mol À1 ; 1.7 kcal mol À1 per CÀC bond); the heats of formation for 1-3 computed according to homodesmotic equations are 52, 35, and 4 kcal mol…”

The intramolecular Diels–Alder reaction: recent advances and synthetic applications

“…A related cyclization is being studied in an approach to sinularene (191) from 295 and a fused cyclopentadiene 296 plays a key role in a route being developed to capnellene (195). An early stage of the recently completed total synthesis of dodecahedrane (193) depends upon the cyclization of 297 (192). An alternative solution to the pestiferous cyclopentadiene rearrangement problem is to use a suitable blocking group, although chlorine was found to be unsatisfactory (198).…”

Diels-Alder Reactions of 12-Hydroxy-9(10®20)-5aH-abeo-abieta-1(10),8(9),12(13)-triene-11,14-dione

“…Indeed, the more sequential transformations that can occur, the fewer the steps needed to achieve a given total synthesis, and hence the more efficient the synthesis is. Such transformations have been widely studied and are described in the literature either as a cascade, [33] domino, [34] tandem, [35] consecutive, [36] or as an one-pot reaction. It is not surprising that Diels-Alder reactions are particularly useful for multiple bond formations.…”