Synthesis of Specifically Substituted 1‐Azaadamantanes

Abstract

PCMO s CMO s Fig. I . Schematic representation of the most important precmonical MO's of 1 which interact with the T[ orbitals (left), as well as the resulting canonical n orbitals 7a2 and 9b2 (right). been discussed for similar d o nonorthogonal systemsf2]. Semiempirical MO calculations on 1 using a modified INDO methodf3] predict a large o/n interaction. A quantitative analysis according to ref.["i indicates that each of the two high-lying n orbitals of the perimeter interacts considerably with two precanonical o orbitals (PCMO's) (Fig. 1). The resulting canonical n orbitals (CMO's) 7a2 and 9b2I5] are also shown in Figure 1. The d o interaction causes rotation of the pn atomic orbitals at the C(2)/C(5) and C(7)/ C( 10) centers.Assuming that a bromine molecule approaches annulene 1 either parallel (3a) or perpendicular (3b) to the plane of the perimeter the antibonding interaction between the occupied levels of the halogen [for (3a) TI and n*, for (3b) n*and o] and 9b2 and 7a2 in syn-addition is smaller than that in anti-addition. This is shown in Figure 2 for the approach parallel to the plane of the perimeter (3a). The main reason for the above mentioned difference is the smaller overlapi2b1 between the n orbitals at the C(2)/C(5) or C(7)/C( 10) centers of 1 and the corresponding orbitals of bromine in syn-addition compared to anti-addition. The rotation of the CMO's demonstrated in Figure 1 also occurs in the norcaradiene valence tautomer of 1. b , + \ Fig. 2. Qualitative diagram for the interaction between the highest occupied molecular orbitals of Br2 and the C M O S of 1 (7a2 and 9b2) for anti- (left) and syn-addition (right), assuming that Br2 approaches parallel to the plane of the perimeter (see 3a). 936.[5] The calculated o-contribution to both orbitals amounts to 10% (7a2) and 30% (9b2) respectively.

Acylation of Esters, Ketones and Nitriles

“…The reactions can be con-o R = PhCH 2 , vinyl, Me (230) NaH o (231) o (232) trolled in a number of ways to give regioselective products but, in the case of the Dieckmann reaction, regioselectivity is not important if the cyclic ketone, derived by decarboxylation, is required. A Thorpe-Ziegler, retro-Thorpe-Ziegler sequence has been used to a-tetramethylate the bisnitrile (239; Scheme 101).251 3.6.9 CONCLUSIONS The Claisen and Dieckmann reactions and their modifications are major synthetic methods for the formation of acyclic and cyclic systems.…”

The Role of Through-Bond Stereoelectronic Effects in the Reactivity of 3-Azabicyclo[3.3.1]nonanes

“…Interactions in chemistry can occur through-space and/or through-bond, − both of which have been the subject of intense research in theoretical chemistry , and photoelectron spectroscopy. − These interactions can affect reactivity/selectivity of molecules because their manifestations are net stabilizing or destabilizing and depend on molecular geometry, hence stereoelectronic. − For example, many investigations have been sparked by 1-azaadamantane structures (e.g., Scheme , 1 ) because of their unique, conformationally constrained architecture, − rich in hyperconjugation. ,, Additionally, 1-azaadamantanes (and derivatives like 1-azaadamantanones) have been synthesized , and studied in the past for their tendency to undergo Grob fragmentations, for their intramolecular through-bond and charge transfer interactions, and for measuring electron spin distribution through a σ skeleton by 13 C contact shifts in NMR studies . We developed an interest in 1-azaadamantanone structures (e.g., 1 , Scheme ) and their 3-azabicyclo[3.3.1]­nonane fragmentation products (e.g., 4 and 5 , Scheme ) for their visually appealing and unusual structures, which hold functional groups of varying nucleophilicity and electrophilicity in particular orientations.…”

“…11−16 For example, many investigations have been sparked by 1-azaadamantane structures (e.g., Scheme 1, 1) because of their unique, conformationally constrained architecture, 17−19 rich in hyperconjugation. 11,20,21 Additionally, 1-azaadamantanes (and derivatives like 1-azaadamantanones) have been synthesized 22,23 and studied in the past for their tendency to undergo Grob fragmentations, 24 for their intramolecular through-bond 16 and charge transfer interactions, 25 and for measuring electron spin distribution through a σ skeleton by 13 C contact shifts in NMR studies. 26 We developed an interest in 1-azaadamantanone structures (e.g., 1, Scheme 1) and their 3-azabicyclo[3.3.1]nonane fragmentation products (e.g., 4 and 5, Scheme 1) for their visually appealing 27 and unusual structures, which hold functional groups of varying nucleophilicity and electrophilicity in particular orientations.…”

The Role of Through-Bond Stereoelectronic Effects in the Reactivity of 3-Azabicyclo[3.3.1]nonanes

“…[11][12][13][14][15][16] For example, many investigations have been sparked by 1azaadamantane structures (e.g., Scheme 1, 1) because of its unique, conformationally constrained architecture, [17][18][19] rich in hyperconjugation. 11,20,21 Additionally, 1-azaadamantanes (and derivatives like 1-azaadamantanones) have been synthesized 22,23 and studied in the past for their tendency to undergo Grob fragmentations, 24 for their intramolecular through-bond 16 and charge transfer interactions, 25 and for measuring electron spin distribution through a -skeleton by 13 C contact shifts in NMR studies. 26 We developed an interest in 1-azaadamantanone structures (e.g., 1, Scheme 1) and their 3-azabicyclo [3.3.1]nonane fragmentation products (e.g., 4 and 5, Scheme 1) for their visually appealing 27 and unusual structures, which hold functional groups of varying nucleophilicity and electrophilicity in particular orientations.…”