<i>trans</i>-RhCl(CO)(PPh₃)₂-Catalyzed Monomeric and Dimeric Cycloisomerization of Propargylic 2,3-Dienoates. Establishment of α,β-Unsaturated δ-Lactone Rings by Cyclometallation

Cyclometallation of two unsaturated carbon−carbon bonds usually requires the application of low-valent metal catalysts, which could cleave the propargylic ester linkage. Thus, it is desirable to identify a catalyst which could undergo cyclometallation without cleaving the propargylic ester linkage. In this paper, we used trans-RhCl(CO)(PPh3)2 to realize the cyclometallation of propargylic 2,3-dienoates. The substituents at the 4-position of allenoate moiety nicely control the reaction pathway:  when the 4-position of propargylic 2,3-dienoate 1 was monosubstituted with an aryl group, the bicyclic intermediate 7 formed by the cyclometallation could highly selectively undergo carbometalation with the alkyne moiety in the second molecule of propargylic 2,3-dienoate 1 to afford metallabicyclic intermediates 8a or 8b. Subsequent reductive elimination would afford 9, which could undergo an intramolecular Diels−Alder reaction resulting in the formation of polycyclic bis(δ-lactone)-containing structures 2. The intermediate could be trapped by adding 3-methoxyprop-1-yne affording cyclization−aromatization product 4p highly selectively. If the substituent at the 4-positon of the 2,3-allenoate moiety has a β-H atom, sequential unimolecular cyclometallation/β-H elimination/reductive elimination occurs to afford cross-conjugated 5(Z)-alkylidene-4-alkenyl-5,6-dihydropyran-2-ones. The Z-stereochemistry of the exo double bond was determined by the cyclometallation. Some of the α,β-unsaturated δ-lactones could be easily converted to other synthetically useful compounds via reduction reaction, hydrogenation, and iodination/coupling protocol

<i>trans</i>-RhCl(CO)(PPh₃)₂-Catalyzed Monomeric and Dimeric Cycloisomerization of Propargylic 2,3-Dienoates. Establishment of α,β-Unsaturated δ-Lactone Rings by Cyclometallation

Cyclometallation of two unsaturated carbon−carbon bonds usually requires the application of low-valent metal catalysts, which could cleave the propargylic ester linkage. Thus, it is desirable to identify a catalyst which could undergo cyclometallation without cleaving the propargylic ester linkage. In this paper, we used trans-RhCl(CO)(PPh3)2 to realize the cyclometallation of propargylic 2,3-dienoates. The substituents at the 4-position of allenoate moiety nicely control the reaction pathway:  when the 4-position of propargylic 2,3-dienoate 1 was monosubstituted with an aryl group, the bicyclic intermediate 7 formed by the cyclometallation could highly selectively undergo carbometalation with the alkyne moiety in the second molecule of propargylic 2,3-dienoate 1 to afford metallabicyclic intermediates 8a or 8b. Subsequent reductive elimination would afford 9, which could undergo an intramolecular Diels−Alder reaction resulting in the formation of polycyclic bis(δ-lactone)-containing structures 2. The intermediate could be trapped by adding 3-methoxyprop-1-yne affording cyclization−aromatization product 4p highly selectively. If the substituent at the 4-positon of the 2,3-allenoate moiety has a β-H atom, sequential unimolecular cyclometallation/β-H elimination/reductive elimination occurs to afford cross-conjugated 5(Z)-alkylidene-4-alkenyl-5,6-dihydropyran-2-ones. The Z-stereochemistry of the exo double bond was determined by the cyclometallation. Some of the α,β-unsaturated δ-lactones could be easily converted to other synthetically useful compounds via reduction reaction, hydrogenation, and iodination/coupling protocol

Construction of Thioamide Peptide via Sulfur-Involved Amino Acids/Amino Aldehydes Coupling

A sulfur-involved ligation for thioamide quasi-peptides was developed via amino acids and amino aldehydes coupling. The key to the transformation was the chelation of copper with imines for chiral activation and fixation. In this environment, linear polysulfur decreased the alkalinity of single sulfur anions to prevent racemization caused by the interaction between sulfur and sodium sulfide. Dipeptides, tripeptides, tetrapeptides, and the linkage between the drug and amino acids were successfully obtained

<i>trans</i>-RhCl(CO)(PPh₃)₂-Catalyzed Monomeric and Dimeric Cycloisomerization of Propargylic 2,3-Dienoates. Establishment of α,β-Unsaturated δ-Lactone Rings by Cyclometallation

Cyclometallation of two unsaturated carbon−carbon bonds usually requires the application of low-valent metal catalysts, which could cleave the propargylic ester linkage. Thus, it is desirable to identify a catalyst which could undergo cyclometallation without cleaving the propargylic ester linkage. In this paper, we used trans-RhCl(CO)(PPh3)2 to realize the cyclometallation of propargylic 2,3-dienoates. The substituents at the 4-position of allenoate moiety nicely control the reaction pathway:  when the 4-position of propargylic 2,3-dienoate 1 was monosubstituted with an aryl group, the bicyclic intermediate 7 formed by the cyclometallation could highly selectively undergo carbometalation with the alkyne moiety in the second molecule of propargylic 2,3-dienoate 1 to afford metallabicyclic intermediates 8a or 8b. Subsequent reductive elimination would afford 9, which could undergo an intramolecular Diels−Alder reaction resulting in the formation of polycyclic bis(δ-lactone)-containing structures 2. The intermediate could be trapped by adding 3-methoxyprop-1-yne affording cyclization−aromatization product 4p highly selectively. If the substituent at the 4-positon of the 2,3-allenoate moiety has a β-H atom, sequential unimolecular cyclometallation/β-H elimination/reductive elimination occurs to afford cross-conjugated 5(Z)-alkylidene-4-alkenyl-5,6-dihydropyran-2-ones. The Z-stereochemistry of the exo double bond was determined by the cyclometallation. Some of the α,β-unsaturated δ-lactones could be easily converted to other synthetically useful compounds via reduction reaction, hydrogenation, and iodination/coupling protocol

Opto-thermal dynamics in whispering-gallery microresonators

Optical whispering-gallery-mode microresonators with ultrahigh quality factors and small mode volumes have played an important role in modern physics. They have been demonstrated as a diverse platform for a wide range of photonics applications, such as nonlinear optics, optomechanics, quantum optics, and information processing. Thermal behaviors induced by power buildup in resonators or environmental perturbations are ubiquitous in high-quality-factor whispering-gallery-mode resonators and have played an important role in their operation for various applications. Here in this review, we discuss the mechanisms of laser field induced thermal nonlinear effects, including thermal bistability and thermal oscillation. With the help of the thermal bistability effect, optothermal spectroscopy and optical non-reciprocity have been demonstrated. On the other hand, by tuning the temperature of the environment, the resonant mode frequency will shift, which could also be used for thermal sensing/tuning applications. Thermal locking technique and thermal imaging mechanisms are discussed briefly. Last, we review some techniques to realize thermal stability in a high-quality-factor resonator system

<i>trans</i>-RhCl(CO)(PPh₃)₂-Catalyzed Monomeric and Dimeric Cycloisomerization of Propargylic 2,3-Dienoates. Establishment of α,β-Unsaturated δ-Lactone Rings by Cyclometallation

Cyclometallation of two unsaturated carbon−carbon bonds usually requires the application of low-valent metal catalysts, which could cleave the propargylic ester linkage. Thus, it is desirable to identify a catalyst which could undergo cyclometallation without cleaving the propargylic ester linkage. In this paper, we used trans-RhCl(CO)(PPh3)2 to realize the cyclometallation of propargylic 2,3-dienoates. The substituents at the 4-position of allenoate moiety nicely control the reaction pathway:  when the 4-position of propargylic 2,3-dienoate 1 was monosubstituted with an aryl group, the bicyclic intermediate 7 formed by the cyclometallation could highly selectively undergo carbometalation with the alkyne moiety in the second molecule of propargylic 2,3-dienoate 1 to afford metallabicyclic intermediates 8a or 8b. Subsequent reductive elimination would afford 9, which could undergo an intramolecular Diels−Alder reaction resulting in the formation of polycyclic bis(δ-lactone)-containing structures 2. The intermediate could be trapped by adding 3-methoxyprop-1-yne affording cyclization−aromatization product 4p highly selectively. If the substituent at the 4-positon of the 2,3-allenoate moiety has a β-H atom, sequential unimolecular cyclometallation/β-H elimination/reductive elimination occurs to afford cross-conjugated 5(Z)-alkylidene-4-alkenyl-5,6-dihydropyran-2-ones. The Z-stereochemistry of the exo double bond was determined by the cyclometallation. Some of the α,β-unsaturated δ-lactones could be easily converted to other synthetically useful compounds via reduction reaction, hydrogenation, and iodination/coupling protocol

Ligand-Controlled Divergent Cross-Coupling Involving Organosilicon Compounds for Thioether and Thioester Synthesis

A divergent cross-coupling for both thioether and thioester construction from organosilicon compounds has been developed. Predominant selectivity for Hiyama-type coupling and C1 insertion reaction was achieved under the guidance of ligands. Thioether was obtained under ligand-free conditions in which disulfide generated from homocoupling could be prevented. Meanwhile, application of bidentate phosphine ligands under carbon monoxide atmosphere (CO balloon) afforded the thioester with little decomposition, which was revealed through interval NMR tracking

<i>trans</i>-RhCl(CO)(PPh₃)₂-Catalyzed Monomeric and Dimeric Cycloisomerization of Propargylic 2,3-Dienoates. Establishment of α,β-Unsaturated δ-Lactone Rings by Cyclometallation

Cyclometallation of two unsaturated carbon−carbon bonds usually requires the application of low-valent metal catalysts, which could cleave the propargylic ester linkage. Thus, it is desirable to identify a catalyst which could undergo cyclometallation without cleaving the propargylic ester linkage. In this paper, we used trans-RhCl(CO)(PPh3)2 to realize the cyclometallation of propargylic 2,3-dienoates. The substituents at the 4-position of allenoate moiety nicely control the reaction pathway:  when the 4-position of propargylic 2,3-dienoate 1 was monosubstituted with an aryl group, the bicyclic intermediate 7 formed by the cyclometallation could highly selectively undergo carbometalation with the alkyne moiety in the second molecule of propargylic 2,3-dienoate 1 to afford metallabicyclic intermediates 8a or 8b. Subsequent reductive elimination would afford 9, which could undergo an intramolecular Diels−Alder reaction resulting in the formation of polycyclic bis(δ-lactone)-containing structures 2. The intermediate could be trapped by adding 3-methoxyprop-1-yne affording cyclization−aromatization product 4p highly selectively. If the substituent at the 4-positon of the 2,3-allenoate moiety has a β-H atom, sequential unimolecular cyclometallation/β-H elimination/reductive elimination occurs to afford cross-conjugated 5(Z)-alkylidene-4-alkenyl-5,6-dihydropyran-2-ones. The Z-stereochemistry of the exo double bond was determined by the cyclometallation. Some of the α,β-unsaturated δ-lactones could be easily converted to other synthetically useful compounds via reduction reaction, hydrogenation, and iodination/coupling protocol

<i>trans</i>-RhCl(CO)(PPh₃)₂-Catalyzed Monomeric and Dimeric Cycloisomerization of Propargylic 2,3-Dienoates. Establishment of α,β-Unsaturated δ-Lactone Rings by Cyclometallation

Cyclometallation of two unsaturated carbon−carbon bonds usually requires the application of low-valent metal catalysts, which could cleave the propargylic ester linkage. Thus, it is desirable to identify a catalyst which could undergo cyclometallation without cleaving the propargylic ester linkage. In this paper, we used trans-RhCl(CO)(PPh3)2 to realize the cyclometallation of propargylic 2,3-dienoates. The substituents at the 4-position of allenoate moiety nicely control the reaction pathway:  when the 4-position of propargylic 2,3-dienoate 1 was monosubstituted with an aryl group, the bicyclic intermediate 7 formed by the cyclometallation could highly selectively undergo carbometalation with the alkyne moiety in the second molecule of propargylic 2,3-dienoate 1 to afford metallabicyclic intermediates 8a or 8b. Subsequent reductive elimination would afford 9, which could undergo an intramolecular Diels−Alder reaction resulting in the formation of polycyclic bis(δ-lactone)-containing structures 2. The intermediate could be trapped by adding 3-methoxyprop-1-yne affording cyclization−aromatization product 4p highly selectively. If the substituent at the 4-positon of the 2,3-allenoate moiety has a β-H atom, sequential unimolecular cyclometallation/β-H elimination/reductive elimination occurs to afford cross-conjugated 5(Z)-alkylidene-4-alkenyl-5,6-dihydropyran-2-ones. The Z-stereochemistry of the exo double bond was determined by the cyclometallation. Some of the α,β-unsaturated δ-lactones could be easily converted to other synthetically useful compounds via reduction reaction, hydrogenation, and iodination/coupling protocol

<i>trans</i>-RhCl(CO)(PPh₃)₂-Catalyzed Monomeric and Dimeric Cycloisomerization of Propargylic 2,3-Dienoates. Establishment of α,β-Unsaturated δ-Lactone Rings by Cyclometallation

Cyclometallation of two unsaturated carbon−carbon bonds usually requires the application of low-valent metal catalysts, which could cleave the propargylic ester linkage. Thus, it is desirable to identify a catalyst which could undergo cyclometallation without cleaving the propargylic ester linkage. In this paper, we used trans-RhCl(CO)(PPh3)2 to realize the cyclometallation of propargylic 2,3-dienoates. The substituents at the 4-position of allenoate moiety nicely control the reaction pathway:  when the 4-position of propargylic 2,3-dienoate 1 was monosubstituted with an aryl group, the bicyclic intermediate 7 formed by the cyclometallation could highly selectively undergo carbometalation with the alkyne moiety in the second molecule of propargylic 2,3-dienoate 1 to afford metallabicyclic intermediates 8a or 8b. Subsequent reductive elimination would afford 9, which could undergo an intramolecular Diels−Alder reaction resulting in the formation of polycyclic bis(δ-lactone)-containing structures 2. The intermediate could be trapped by adding 3-methoxyprop-1-yne affording cyclization−aromatization product 4p highly selectively. If the substituent at the 4-positon of the 2,3-allenoate moiety has a β-H atom, sequential unimolecular cyclometallation/β-H elimination/reductive elimination occurs to afford cross-conjugated 5(Z)-alkylidene-4-alkenyl-5,6-dihydropyran-2-ones. The Z-stereochemistry of the exo double bond was determined by the cyclometallation. Some of the α,β-unsaturated δ-lactones could be easily converted to other synthetically useful compounds via reduction reaction, hydrogenation, and iodination/coupling protocol