Synthesis of Axially Chiral Biaryls through Cobalt(II)-Catalyzed Atroposelective C-H Arylation.

Highly efficient synthesis of axially chiral biaryl amines through cobalt-catalyzed atroposelective C-H arylation using easily accessible cobalt(II) salt and salicyloxazoline ligand has been reported. This methodology provides a straightforward and sustainable access to a broad range of enantioenriched biaryl-2-amines in good yields (up to 99 %) with excellent enantioselectivities (up to 99 % ee). The synthetic utility of the unprecedented method is highlighted by its scalability and diverse transformations.

Brønsted Acid-Catalyzed Formal (3+3)-Annulation of Propargylic (Aza)-para-Quinone Methides with 4-Hydroxycoumarins and 1,3-Dicarbonyl Compounds.

Herein, we describe a highly effective 1,8-conjugate-addition-mediated formal (3+3)-annulation of (aza)-para-quinone methides in situ generated from propargylic alcohols with 4-hydroxycoumarins and 1,3-dicarbonyl compounds under the catalysis of a Brønsted acid. This methodology affords efficient and practical access to synthetically important and highly functionalized pyranocoumarins and pyrans in excellent yields under mild conditions. Importantly, these products exhibit impressive inhibitory activity toward α-glucosidase.

Copper-catalyzed monoselective C-H amination of ferrocenes with alkylamines.

A copper-catalyzed mono-selective C-H amination of ferrocenes assisted by 8-aminoquinoline is presented here. A range of amines, including bioactive molecules, were successfully installed to the ortho-position of ferrocene amides with high efficiency under mild conditions. A range of functionalized ferrocenes were compatible to give the aminated products in moderate to good yields. The gram-scale reaction was smoothly conducted and the directing group could be removed easily under basic conditions.

Transmission of single-carrier 400G signals (515.2-Gb/s) based on 128.8-GBaud PDM QPSK over 10,130- and 6,078 km terrestrial fiber links.

We experimentally demonstrate the coherent transmission system with the highest ETDM-based symbol rate of 128.8-GBaud over record breaking distances. We successfully transmitted single-carrier 515.2-Gb/s PDM-QPSK/9-QAM signals over 10,130km/6,078-km, respectively, over 100km spans of TeraWave SLA + fiber. To the best of our knowledge, it is the highest ETDM-based symbol rate reported so far, and the longest WDM transmission distance with single-carrier 400G signals. For the first time, the 515.2-Gb/s single-carrier PDM-QPSK signals in 200-GHz-grid are successfully transmitted over distance above 10,000km in terrestrial transmission environment. We have also demonstrated the transmission of single carrier 128.8-GBaud filtered QPSK signals in 100-GHz-grid over 6,078-km, which has the line spectral efficiency (SE) of 5.152 (b/s/Hz).

Experimental demonstration of iterative post-equalization algorithm for 37.5-Gbaud PM-16QAM quad-carrier Terabit superchannel.

We experimentally demonstrate a quad-carrier 1-Tb/s solution with 37.5-GBaud PM-16QAM signal over 37.5-GHz optical grid at 6.7 b/s/Hz net spectral efficiency. Digital Nyquist pulse shaping at the transmitter and post-equalization at the receiver are employed to mitigate the impairments of joint inter-symbol-interference (ISI) and inter-channel-interference (ICI) symbol degradation. The post-equalization algorithms consist of one sample/symbol based decision-directed least mean square (DD-LMS) adaptive filter, digital post filter and maximum likelihood sequence estimation (MLSE), and a positive iterative process among them. By combining these algorithms, the improvement as much as 4-dB OSNR (0.1nm) at SD-FEC limit (Q(2) = 6.25 corresponding to BER = 2.0e-2) is obtained when compared to no such post-equalization process, and transmission over 820-km EDFA-only standard single-mode fiber (SSMF) link is achieved for two 1.2-Tb/s signals with the averaged Q(2) factor larger than 6.5 dB for all sub-channels. Additionally, 50-GBaud 16QAM operating at 1.28 samples/symbol in a DAC is also investigated and successful transmission over 410-km SSMF link is achieved at 62.5-GHz optical grid.

Performance comparison of spectrum-narrowing equalizations with maximum likelihood sequence estimation and soft-decision output.

Maximum likelihood sequence estimation (MLSE) offers effective equalizations for bandwidth-limited optical signal on mitigation towards inter-symbol-interference (ISI) impairment. In this paper, we provide the first comprehensive comparisons and analysis of three post-compensation algorithms on the same modeling platform for high spectral-efficiency (SE) optical systems employing the spectral prefiltering. Those algorithms include 1-tap constant modulus algorithm (CMA) and 3-tap MLSE, regular CMA and digital filter with 2-tap MLSE, and constant multi-modulus algorithm (CMMA) with 2-tap MLSE. Furthermore, a novel and effective approach is proposed and verified for the generation of both hard value and soft value at the output of MLSE in order to be compatible with the implementation of soft-decision forward error correction (SD-FEC) decoding process.

Optical independent-sideband modulation for bandwidth-economic coherent transmission.

We proposed and implemented a bandwidth-economic coherent optical transmission technology using optical independent-sideband (O-ISB) modulation. Generation of two software-defined, 30-GBd O-ISB channels per wavelength sharing one set of transmitter hardware was demonstrated, which was made possible by digital single-sided up-conversion, channel pre-equalization and optical IQ modulation with precise amplitude and delay matching between driving signals. With 120-Gb/s PM-QPSK per O-ISB channel, we successfully delivered 16 O-ISB channels in 8 wavelengths at 3.86-bits/s/Hz over 2100 km SSMF. In addition, the system performance was evaluated by using regular and enhanced Rx DSP, respectively. For metro and regional network applications where small footprint, low power consumption and low cost are required features, the proposed two-channels-per-wavelength O-ISB modulation may be considered an economic option.

Transmission of 8 × 480-Gb/s super-Nyquist-filtering 9-QAM-like signal at 100 GHz-grid over 5000-km SMF-28 and twenty-five 100 GHz-grid ROADMs.

We experimentally demonstrate a highly filtering-tolerant multi-modulus equalization (MMEQ) process for very aggressively spectrum-shaped 9-ary quadrature-amplitude-modulation (9-QAM)-like polarization division multiplexing quadrature phase shift keying (PDM-QPSK) signal to achieve 400-Gb/s wavelength-division-multiplexing (WDM) channels on the 100-GHz grid for ultra-long-haul reach and high tolerance of the filter narrowing effect caused by reconfigurable optical add-drop multiplexers (ROADMs). We successfully transmitted 8 channels 480-Gb/s super-Nyquist (channel occupancy much less than signal baud rate) WDM signals at 100-GHz grid over 25 × 200 km conventional single-mode fiber-28 (SMF-28) with post Raman amplification and 25 ROADMs at a net spectral efficiency (SE) of 4b/s/Hz, after excluding the 20% soft-decision forward-error-correction (FEC) overhead. The system performance is significantly enhanced by the MMEQ based on 9-QAM-like constellations compared to the conventional 4 point QPSK constellation. A record transmission distance over conventional SMF-28 with a large number of ROADMs is firstly reported on the 400-Gb/s channels at 100-GHz grid.

WDM transmission of 108.4-Gbaud PDM-QPSK signals (40 × 433.6-Gb/s) over 2800-km SMF-28 with EDFA-only.

We experimentally demonstrated the transmission of 40 × 433.6-Gb/s Nyquist wavelength-division-multiplexing (N-WDM) optical time-division-multiplexing (OTDM) over 2800-km single-mode fiber (SMF)-28 with Erbium-doped fiber amplifier (EDFA)-only amplification, adopting polarization-division-multiplexing carrier-suppressed return-to-zero quadrature-phase-shift-keying (PDM-CSRZ-QPSK) modulation as well as post filter and 1-bit maximum likelihood sequence estimation (MLSE). Each channel occupies 100 GHz, yielding a spectral efficiency of 4.05 b/s/Hz. The bit-error ratio (BER) of all channels is less than the pre-forward-error-correction (pre-FEC) limit of 3.8 × 10(-3) after 2800-km SMF-28 transmission.

Pd(II)-Catalyzed Atroposelective C-H Allylation: Synthesis of Enantioenriched N-Aryl Peptoid Atropisomers.

A Pd-catalyzed atroposelective C-H allylation with 1,1-disubstituted alkenes was developed for the synthesis of enantioenriched N-aryl peptoid atropisomers via ß-H elimination using commercially available and inexpensive L-pGlu-OH as a chiral ligand. Exclusive allylic selectivity was achieved. Additionally, a series of enantioenriched N-aryl peptoid atropisomers were obtained in synthetically useful yields with excellent enantioselectivities (up to 90% yield and 97% ee).

Palladium-Catalyzed Directed Atroposelective C-H Allylation via ß-H Elimination: 1,1-Disubstituted Alkenes as Allyl Surrogates.

Transition-metal-catalyzed dehydrogenative C-H allylation with 1,1-disubstituted alkenes via ß-H elimination remains challenging, because of the low reactivity and difficulty of controlling selectivity. Herein, the development of a Pd(II)-catalyzed directed atroposelective C-H allylation with methacrylates is described. Exclusive allylic selectivity was achieved. A vast array of axially chiral biaryl-2-amines are efficiently synthesized with excellent enantioselectivities (up to >99% enantiomeric excess).

60 GHz millimeter-wave gigabit wireless services over long-reach passive optical network using remote signal regeneration and upconversion.

This study proposed and experimentally demonstrated a cost-efficient scheme that can deliver 60 GHz millimeter-wave (mm-wave) multi-gigabit wireless services over 125 km long-reach passive optical networks (PONs) without any dispersion compensation. By introducing a remote local exchange (LE) stage with robust signal regeneration and all-optical upconversion functionalities, the proposed long-reach optical-wireless access network can easily accommodate over 128 users with 2.5 Gb/s shared bandwidth as well as shifting the capital expenditure of multiple hybrid optical network units (ONUs) toward single LE headend. Experimental verification shows that the power penalties for wireless and wired services are 1.8 dB and 0.4 dB at 10(-9) BER after 125 km optical fiber transmission.